diff --git a/pyproject.toml b/pyproject.toml
index aa541c3..e4b56ef 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "poetry.core.masonry.api"
 
 [tool.poetry]
 name = "webdiff"
-version = "1.3.0b1"
+version = "1.3.0b2"
 description = "Two-column web-based git difftool"
 license = "Apache-2.0"
 readme = "README.md"
diff --git a/testdata/jsondiffs/left/ospd5.summary.json b/testdata/jsondiffs/left/ospd5.summary.json
new file mode 100644
index 0000000..faca24c
--- /dev/null
+++ b/testdata/jsondiffs/left/ospd5.summary.json
@@ -0,0 +1 @@
+{"id":8503055,"num_reps":5505497728300038000000,"elapsed_s":27775981.582439058,"failures":["sredetiltnapsres","stngeiaedrlpsdes","gresenapdtilsres","dresenalstipares","gresenalstipares","gresenalstipores","dresenilstapares","dresenilstapores","dresenilstapures","gressnaletipdres","gntseaieslrdopes","sttseiaenrlpsges","plsdeaiertnrsges","plsteaiertnrsges","psldeaiertnrsges","spldeaiertnrsges","spldeiaetrntsges","splseaiertnrsdes","splseaiertnrsges","slpseaierntrsdes","slpseaierntrsges","slpseaiertnrsges","slpseiaerntrsdes","dresenapstilares","gresenapstilares","gresenapstilores","dplcseainrtngies","dresenilgtapsres","stndeiaenrlpsges","stngeiaenrlpsges","gsedtnileratspes","slpseaierntrgdes","gntseaieplrdseas","gntseaieplrdsees","plcdeaiertnrsges","dplseaiertnrsges","mplseaiertnrsges","sresetipdnalsges","plcseaiertnrsges","dlpseaiertnrsges","gredenalstipares","gredenalstipores","hsebetalsripgnes","hsedetalsripgnes","tsebetalsripgnes","tsedetalsripgnes"],"elim_level":[0,15455,177058,5063716,76688548,461765945,746413471,1341313341,1163044169,683351596,332798842,146849412,75414967,51931121],"secs_by_level":[3674055.3433500067,410511.63218999945,1173934.825350049,3012839.132659852,5235705.436329976,4241101.513749921,4354658.159489981,2102788.1823800365,669439.2463199788,109737.61249999885,25531.954199997952,4647.2012399998175,1373.4651100000929],"bounds":[17529004948,13770052786,11002135202,8716185865,6917888192,5476876187,4192563351,3051811248,2128082619,1431049972,956438815,668040946,500412197],"depth":[0,19950,615593,14344534,148852615,670318189,1798495841,2584907222,2213849795,1122244756,511943456,205264471,96606475,62028585],"boards_to_test":16527857205,"init_nodes":21169090330328,"total_nodes":216126848966789,"tree_bytes":426388045692928,"total_bytes":574688434585600,"n_bound":9429491482,"n_force":2101423756,"max_multi":1312378509,"bound_secs":[0,26.31909999999997,762.3841000000707,13895.171989995355,96300.35142999486,278184.6050899924,509398.4086700136,489545.5812600387,261858.04687000782,96741.63683000114,42098.825499994186,16502.548799997923,8129.411579999221,6838.873439999473],"test_secs":859209.9650399276,"best_board":[3827,"splseaiertnrsges"]}
diff --git a/testdata/jsondiffs/right/ospd5.summary.json b/testdata/jsondiffs/right/ospd5.summary.json
new file mode 100644
index 0000000..c6d6c96
--- /dev/null
+++ b/testdata/jsondiffs/right/ospd5.summary.json
@@ -0,0 +1,144 @@
+{
+  "id": 8503055,
+  "num_reps": 5505497728300038000000,
+  "elapsed_s": 27775981.582439058,
+  "failures": [
+    "sredetiltnapsres",
+    "stngeiaedrlpsdes",
+    "gresenapdtilsres",
+    "dresenalstipares",
+    "gresenalstipares",
+    "gresenalstipores",
+    "dresenilstapares",
+    "dresenilstapores",
+    "dresenilstapures",
+    "gressnaletipdres",
+    "gntseaieslrdopes",
+    "sttseiaenrlpsges",
+    "plsdeaiertnrsges",
+    "plsteaiertnrsges",
+    "psldeaiertnrsges",
+    "spldeaiertnrsges",
+    "spldeiaetrntsges",
+    "splseaiertnrsdes",
+    "splseaiertnrsges",
+    "slpseaierntrsdes",
+    "slpseaierntrsges",
+    "slpseaiertnrsges",
+    "slpseiaerntrsdes",
+    "dresenapstilares",
+    "gresenapstilares",
+    "gresenapstilores",
+    "dplcseainrtngies",
+    "dresenilgtapsres",
+    "stndeiaenrlpsges",
+    "stngeiaenrlpsges",
+    "gsedtnileratspes",
+    "slpseaierntrgdes",
+    "gntseaieplrdseas",
+    "gntseaieplrdsees",
+    "plcdeaiertnrsges",
+    "dplseaiertnrsges",
+    "mplseaiertnrsges",
+    "sresetipdnalsges",
+    "plcseaiertnrsges",
+    "dlpseaiertnrsges",
+    "gredenalstipares",
+    "gredenalstipores",
+    "hsebetalsripgnes",
+    "hsedetalsripgnes",
+    "tsebetalsripgnes",
+    "tsedetalsripgnes"
+  ],
+  "elim_level": [
+    0,
+    15455,
+    177058,
+    5063716,
+    76688548,
+    461765945,
+    746413471,
+    1341313341,
+    1163044169,
+    683351596,
+    332798842,
+    146849412,
+    75414967,
+    51931121
+  ],
+  "secs_by_level": [
+    3674055.3433500067,
+    410511.63218999945,
+    1173934.825350049,
+    3012839.132659852,
+    5235705.436329976,
+    4241101.513749921,
+    4354658.159489981,
+    2102788.1823800365,
+    669439.2463199788,
+    109737.61249999885,
+    25531.954199997952,
+    4647.2012399998175,
+    1373.4651100000929
+  ],
+  "bounds": [
+    17529004948,
+    13770052786,
+    11002135202,
+    8716185865,
+    6917888192,
+    5476876187,
+    4192563351,
+    3051811248,
+    2128082619,
+    1431049972,
+    956438815,
+    668040946,
+    500412197
+  ],
+  "depth": [
+    0,
+    19950,
+    615593,
+    14344534,
+    148852615,
+    670318189,
+    1798495841,
+    2584907222,
+    2213849795,
+    1122244756,
+    511943456,
+    205264471,
+    96606475,
+    62028585
+  ],
+  "boards_to_test": 16527857205,
+  "init_nodes": 21169090330328,
+  "total_nodes": 216126848966789,
+  "tree_bytes": 426388045692928,
+  "total_bytes": 574688434585600,
+  "n_bound": 9429491482,
+  "n_force": 2101423756,
+  "max_multi": 1312378509,
+  "bound_secs": [
+    0,
+    26.31909999999997,
+    762.3841000000707,
+    13895.171989995355,
+    96300.35142999486,
+    278184.6050899924,
+    509398.4086700136,
+    489545.5812600387,
+    261858.04687000782,
+    96741.63683000114,
+    42098.825499994186,
+    16502.548799997923,
+    8129.411579999221,
+    6838.873439999473
+  ],
+  "test_secs": 859209.9650399276,
+  "best_board": [
+    3827,
+    "splseaiertnrsges"
+  ]
+}
diff --git a/testdata/jsondiffs/right/tsconfig.json b/testdata/jsondiffs/right/tsconfig.json
index 4971d4b..79a6927 100644
--- a/testdata/jsondiffs/right/tsconfig.json
+++ b/testdata/jsondiffs/right/tsconfig.json
@@ -1,6 +1,6 @@
 {
+  /* Note that this file isn't really JSON! It's JSONC. */
   "compilerOptions": {
-    /* Note that this file isn't really JSON! */
 
     /* Basic Options */
     // "incremental": true,                   /* Enable incremental compilation */
@@ -8,7 +8,7 @@
     "module": "ESNext" /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', 'es2020', or 'ESNext'. */,
     /* Specify library files to be included in the compilation. */
     "lib": [
-      "es2021", 
+      "es2021",
       "dom"
     ] ,
     // "allowJs": true,                       /* Allow javascript files to be compiled. */
diff --git a/ts/CodeDiffContainer.tsx b/ts/CodeDiffContainer.tsx
index 7aa8ac1..05d93ce 100644
--- a/ts/CodeDiffContainer.tsx
+++ b/ts/CodeDiffContainer.tsx
@@ -1,5 +1,5 @@
 import React from 'react';
-import {DiffOptions, encodeDiffOptions} from './diff-options';
+import {GitDiffOptions, gitDiffOptionsToFlags} from './diff-options';
 import {CodeDiff, PatchOptions} from './codediff/codediff';
 import {guessLanguageUsingContents, guessLanguageUsingFileName} from './codediff/language';
 import {GitConfig} from './options';
@@ -53,18 +53,19 @@ export interface ImageDiffData {
 }
 
 // A "no changes" sign which only appears when applicable.
-export function NoChanges(props: {filePair: FilePair}) {
-  const {filePair} = props;
+export function NoChanges(props: {filePair: FilePair; isEqualAfterNormalization: boolean}) {
+  const {filePair, isEqualAfterNormalization} = props;
+  let msg = null;
   if (filePair.no_changes) {
-    return <div className="no-changes">(File content is identical)</div>;
+    msg = <>(File content is identical)</>;
+  } else if (isEqualAfterNormalization) {
+    msg = <>(File content is identical after normalization)</>;
   } else if (filePair.is_image_diff && filePair.are_same_pixels) {
-    return (
-      <div className="no-changes">
-        Pixels are the same, though file content differs (perhaps the headers are different?)
-      </div>
+    msg = (
+      <>Pixels are the same, though file content differs (perhaps the headers are different?)</>
     );
   }
-  return null;
+  return msg ? <div className="no-changes">{msg}</div> : null;
 }
 
 // Either side can be empty (i.e. an add or a delete), in which case getOrNull resolves to null.
@@ -84,7 +85,7 @@ async function getOrNull(side: string, path: string, normalizeJSON: boolean) {
 
 export interface CodeDiffContainerProps {
   filePair: FilePair;
-  diffOptions: Partial<DiffOptions>;
+  diffOptions: Partial<GitDiffOptions>;
   normalizeJSON: boolean;
 }
 
@@ -96,6 +97,8 @@ export function CodeDiffContainer(props: CodeDiffContainerProps) {
   >();
 
   React.useEffect(() => {
+    // It would be more correct to set contents=undefined here to get a loading state,
+    // but this produces an unnecessary flash for rapid transitions.
     const getDiff = async () => {
       const response = await fetch(`/diff/${filePair.idx}`, {
         method: 'POST',
@@ -104,7 +107,7 @@ export function CodeDiffContainer(props: CodeDiffContainerProps) {
           'Content-Type': 'application/json',
         },
         body: JSON.stringify({
-          options: encodeDiffOptions(diffOptions),
+          options: gitDiffOptionsToFlags(diffOptions),
           normalize_json: normalizeJSON,
         }),
       });
@@ -127,6 +130,10 @@ export function CodeDiffContainer(props: CodeDiffContainerProps) {
     });
   }, [filePair, diffOptions, normalizeJSON]);
 
+  const isEqualAfterNormalization = React.useMemo(() => {
+    return !filePair.no_changes && normalizeJSON && contents && contents.before == contents.after;
+  }, [contents, filePair.no_changes, normalizeJSON]);
+
   return (
     <div>
       <div key={filePair.idx}>
@@ -136,6 +143,7 @@ export function CodeDiffContainer(props: CodeDiffContainerProps) {
             contentsBefore={contents.before}
             contentsAfter={contents.after}
             diffOps={contents.diffOps}
+            isEqualAfterNormalization={!!isEqualAfterNormalization}
           />
         ) : (
           'Loading…'
@@ -150,6 +158,7 @@ interface FileDiffProps {
   contentsBefore: string | null;
   contentsAfter: string | null;
   diffOps: DiffRange[];
+  isEqualAfterNormalization: boolean;
 }
 
 function extractFilename(path: string) {
@@ -164,7 +173,7 @@ function lengthOrZero(data: unknown[] | string | null | undefined) {
 }
 
 function FileDiff(props: FileDiffProps) {
-  const {filePair, contentsBefore, contentsAfter, diffOps} = props;
+  const {filePair, contentsBefore, contentsAfter, diffOps, isEqualAfterNormalization} = props;
   const pathBefore = filePair.a;
   const pathAfter = filePair.b;
   // build the diff view and add it to the current DOM
@@ -201,7 +210,7 @@ function FileDiff(props: FileDiffProps) {
 
   return (
     <div className="diff">
-      <NoChanges filePair={filePair} />
+      <NoChanges filePair={filePair} isEqualAfterNormalization={isEqualAfterNormalization} />
       <CodeDiff
         beforeText={contentsBefore}
         afterText={contentsAfter}
diff --git a/ts/DiffOptions.tsx b/ts/DiffOptions.tsx
index 5b5cd34..b870cec 100644
--- a/ts/DiffOptions.tsx
+++ b/ts/DiffOptions.tsx
@@ -1,15 +1,15 @@
 import React from 'react';
 
-import {DiffAlgorithm, DiffOptions, encodeDiffOptions} from './diff-options';
+import {DiffAlgorithm, gitDiffOptionsToFlags} from './diff-options';
 import {PageCover} from './codediff/PageCover';
 import {isLegitKeypress} from './file_diff';
+import {Options, UpdateOptionsFn} from './options';
+import {Unionize} from './utils';
 
 export interface Props {
-  options: Partial<DiffOptions>;
-  setOptions: (newOptions: Partial<DiffOptions>) => void;
+  options: Partial<Options>;
+  updateOptions: UpdateOptionsFn;
   defaultMaxDiffWidth: number;
-  maxDiffWidth: number;
-  setMaxDiffWidth: (maxDiffWidth: number) => void;
   isVisible: boolean;
   setIsVisible: (isVisible: boolean) => void;
 }
@@ -51,47 +51,44 @@ const popupStyle: React.CSSProperties = {
   fontFamily: 'sans-serif',
 };
 
+type BooleanOptions = Extract<Unionize<Options>, {v: boolean}>['k'];
+
 export function DiffOptionsControl(props: Props) {
-  const {options, setOptions, isVisible, setIsVisible, maxDiffWidth, setMaxDiffWidth} = props;
+  const {options, updateOptions, isVisible, setIsVisible} = props;
+  const maxDiffWidth = options.maxDiffWidth ?? props.defaultMaxDiffWidth;
 
   const togglePopup = () => {
     setIsVisible(!isVisible);
   };
-  const toggleIgnoreAllSpace = () => {
-    setOptions({...options, ignoreAllSpace: !options.ignoreAllSpace});
-  };
-  const toggleIgnoreSpaceChange = () => {
-    setOptions({...options, ignoreSpaceChange: !options.ignoreSpaceChange});
-  };
-  const toggleFunctionContext = () => {
-    setOptions({...options, functionContext: !options.functionContext});
+  const toggleField = (k: BooleanOptions) => () => {
+    updateOptions(options => ({[k]: !options[k]}));
   };
   const setUnifiedContext: React.ChangeEventHandler<HTMLInputElement> = e => {
-    setOptions({...options, unified: e.currentTarget.valueAsNumber});
+    updateOptions({unified: e.currentTarget.valueAsNumber});
   };
   const changeDiffAlgorithm: React.ChangeEventHandler<HTMLSelectElement> = e => {
-    setOptions({...options, diffAlgorithm: e.currentTarget.value as DiffAlgorithm});
+    updateOptions({diffAlgorithm: e.currentTarget.value as DiffAlgorithm});
   };
   const changeMaxDiffWidth: React.ChangeEventHandler<HTMLInputElement> = e => {
-    setMaxDiffWidth(e.currentTarget.valueAsNumber);
+    updateOptions({maxDiffWidth: e.currentTarget.valueAsNumber});
   };
 
   React.useEffect(() => {
     const handleKeydown = (e: KeyboardEvent) => {
       if (!isLegitKeypress(e)) return;
       if (e.code == 'KeyW') {
-        setOptions({...options, ignoreAllSpace: !options.ignoreAllSpace});
+        updateOptions(options => ({ignoreAllSpace: !options.ignoreAllSpace}));
       } else if (e.code == 'KeyB') {
-        setOptions({...options, ignoreSpaceChange: !options.ignoreSpaceChange});
+        updateOptions(options => ({ignoreSpaceChange: !options.ignoreSpaceChange}));
       }
     };
     document.addEventListener('keydown', handleKeydown);
     return () => {
       document.removeEventListener('keydown', handleKeydown);
     };
-  }, [options, setOptions]);
+  }, [options, updateOptions]);
 
-  const diffOptsStr = encodeDiffOptions(options).join(' ');
+  const diffOptsStr = gitDiffOptionsToFlags(options).join(' ');
 
   return (
     <>
@@ -108,7 +105,7 @@ export function DiffOptionsControl(props: Props) {
             <table>
               <tbody>
                 <tr>
-                  <td style={{textAlign: 'right', verticalAlign: 'top'}} rowSpan={2}>
+                  <td style={{textAlign: 'right', verticalAlign: 'top'}} rowSpan={3}>
                     Whitespace:
                   </td>
                   <td>
@@ -116,7 +113,7 @@ export function DiffOptionsControl(props: Props) {
                       type="checkbox"
                       checked={!!options.ignoreAllSpace}
                       id="ignore-all-space"
-                      onChange={toggleIgnoreAllSpace}
+                      onChange={toggleField('ignoreAllSpace')}
                     />{' '}
                     <label htmlFor="ignore-all-space">
                       Ignore All Space (<code>git diff -w</code>)
@@ -129,13 +126,24 @@ export function DiffOptionsControl(props: Props) {
                       type="checkbox"
                       checked={!!options.ignoreSpaceChange}
                       id="ignore-space-changes"
-                      onChange={toggleIgnoreSpaceChange}
+                      onChange={toggleField('ignoreSpaceChange')}
                     />{' '}
                     <label htmlFor="ignore-space-changes">
                       Ignore Space Changes (<code>git diff -b</code>)
                     </label>
                   </td>
                 </tr>
+                <tr>
+                  <td>
+                    <input
+                      type="checkbox"
+                      checked={!!options.normalizeJSON}
+                      id="normalize-json"
+                      onChange={toggleField('normalizeJSON')}
+                    />{' '}
+                    <label htmlFor="normalize-json">Normalize JSON</label>
+                  </td>
+                </tr>
                 <tr>
                   <td style={{textAlign: 'right', verticalAlign: 'top'}} rowSpan={2}>
                     Context:
@@ -157,7 +165,7 @@ export function DiffOptionsControl(props: Props) {
                       type="checkbox"
                       checked={!!options.functionContext}
                       id="function-context"
-                      onChange={toggleFunctionContext}
+                      onChange={toggleField('functionContext')}
                     />{' '}
                     <label htmlFor="function-context">
                       Function Context (<code>git diff -W</code>)
diff --git a/ts/DiffView.tsx b/ts/DiffView.tsx
index 926add1..91fc403 100644
--- a/ts/DiffView.tsx
+++ b/ts/DiffView.tsx
@@ -1,6 +1,6 @@
 import React from 'react';
 import {CodeDiffContainer, FilePair} from './CodeDiffContainer';
-import {DiffOptions} from './diff-options';
+import {GitDiffOptions} from './diff-options';
 import {getThickDiff} from './file_diff';
 import {ImageDiff} from './ImageDiff';
 import {ImageDiffMode} from './ImageDiffModeSelector';
@@ -11,11 +11,11 @@ export interface Props {
   thinFilePair: FilePair;
   imageDiffMode: ImageDiffMode;
   pdiffMode: PerceptualDiffMode;
-  diffOptions: Partial<DiffOptions>;
+  diffOptions: Partial<GitDiffOptions>;
   normalizeJSON: boolean;
   changeImageDiffMode: (mode: ImageDiffMode) => void;
   changePDiffMode: React.Dispatch<React.SetStateAction<PerceptualDiffMode>>;
-  changeDiffOptions: (options: Partial<DiffOptions>) => void;
+  changeDiffOptions: (options: Partial<GitDiffOptions>) => void;
 }
 
 export function DiffView(props: Props) {
diff --git a/ts/ImageDiff.tsx b/ts/ImageDiff.tsx
index 639a1df..91e3551 100644
--- a/ts/ImageDiff.tsx
+++ b/ts/ImageDiff.tsx
@@ -119,7 +119,7 @@ export function ImageDiff(props: Props) {
 
   return (
     <div>
-      <div className="image-diff-controls">
+      <div className="diff-mode-controls">
         <ImageDiffModeSelector {...props} />
         <input
           type="checkbox"
@@ -172,7 +172,7 @@ export function ImageDiff(props: Props) {
         </span>
       </div>
       <div className={'image-diff ' + imageDiffMode}>
-        <NoChanges filePair={props.filePair} />
+        <NoChanges filePair={props.filePair} isEqualAfterNormalization={false} />
         {image}
       </div>
     </div>
diff --git a/ts/Root.tsx b/ts/Root.tsx
index ce05f34..5e5ed6e 100644
--- a/ts/Root.tsx
+++ b/ts/Root.tsx
@@ -2,7 +2,6 @@ import React from 'react';
 import {useNavigate, useParams} from 'react-router';
 import {useSearchParams} from 'react-router-dom';
 import {FilePair} from './CodeDiffContainer';
-import {decodeDiffOptions, DiffOptions, encodeDiffOptions} from './diff-options';
 import {DiffView, PerceptualDiffMode} from './DiffView';
 import {FileSelector, FileSelectorMode} from './FileSelector';
 import {isLegitKeypress} from './file_diff';
@@ -10,44 +9,13 @@ import {ImageDiffMode} from './ImageDiffModeSelector';
 import {filePairDisplayName} from './utils';
 import {DiffOptionsControl} from './DiffOptions';
 import {KeyboardShortcuts} from './codediff/KeyboardShortcuts';
-import {GitConfig} from './options';
+import {Options, encodeOptions, GitConfig, parseOptions, UpdateOptionsFn} from './options';
 import {NormalizeJSONOption} from './codediff/NormalizeJSONOption';
 
 declare const pairs: FilePair[];
 declare const initialIdx: number;
 declare const GIT_CONFIG: GitConfig;
 
-interface CombinedOptions extends DiffOptions {
-  maxDiffWidth: number;
-  normalizeJSON?: boolean;
-}
-
-function parseOptions(query: URLSearchParams): Partial<CombinedOptions> {
-  const flags = query.getAll('flag');
-  const diffOptions = decodeDiffOptions(flags);
-  const maxWidthStr = query.get('width');
-  const maxDiffWidth = maxWidthStr ? {maxDiffWidth: Number(maxWidthStr)} : undefined;
-  const normalizeJsonStr = query.get('normalize_json');
-  const normalizeJSON = normalizeJsonStr ? {normalizeJSON: true} : undefined;
-  return {...diffOptions, ...maxDiffWidth, ...normalizeJSON};
-}
-
-function encodeOptions(
-  diffOptions: Partial<DiffOptions>,
-  maxDiffWidth: number,
-  normalizeJSON: boolean,
-) {
-  const flags = encodeDiffOptions(diffOptions);
-  const params = new URLSearchParams(flags.map(f => ['flag', f]));
-  if (maxDiffWidth !== GIT_CONFIG.webdiff.maxDiffWidth) {
-    params.set('width', String(maxDiffWidth));
-  }
-  if (normalizeJSON) {
-    params.set('normalize_json', '1');
-  }
-  return params;
-}
-
 // Webdiff application root.
 export function Root() {
   const [pdiffMode, setPDiffMode] = React.useState<PerceptualDiffMode>('off');
@@ -81,28 +49,22 @@ export function Root() {
   }, [filePair]);
 
   const options = React.useMemo(() => parseOptions(searchParams), [searchParams]);
+  // TODO: merge defaults into options
   const maxDiffWidth = options.maxDiffWidth ?? GIT_CONFIG.webdiff.maxDiffWidth;
   const normalizeJSON = !!options.normalizeJSON;
 
   const setDiffOptions = React.useCallback(
-    (newOptions: Partial<DiffOptions>) => {
-      setSearchParams(encodeOptions(newOptions, maxDiffWidth, normalizeJSON));
-    },
-    [maxDiffWidth, setSearchParams, normalizeJSON],
-  );
-
-  const setMaxDiffWidth = React.useCallback(
-    (newMaxWidth: number) => {
-      setSearchParams(encodeOptions(options, newMaxWidth, normalizeJSON));
+    (newOptions: Partial<Options>) => {
+      setSearchParams(encodeOptions(newOptions));
     },
-    [options, setSearchParams, normalizeJSON],
+    [setSearchParams],
   );
 
-  const setNormalizeJSON = React.useCallback(
-    (newNormalizeJSON: boolean) => {
-      setSearchParams(encodeOptions(options, maxDiffWidth, newNormalizeJSON));
+  const updateOptions = React.useCallback<UpdateOptionsFn>(
+    update => {
+      setDiffOptions({...options, ...(typeof update === 'function' ? update(options) : update)});
     },
-    [options, setSearchParams, maxDiffWidth],
+    [options, setDiffOptions],
   );
 
   // TODO: switch to useKey() or some such
@@ -125,13 +87,15 @@ export function Root() {
         setShowKeyboardHelp(false);
       } else if (e.code === 'Period') {
         setShowOptions(val => !val);
+      } else if (e.code === 'KeyZ') {
+        updateOptions(o => ({normalizeJSON: !o.normalizeJSON}));
       }
     };
     document.addEventListener('keydown', handleKeydown);
     return () => {
       document.removeEventListener('keydown', handleKeydown);
     };
-  }, [idx, selectIndex]);
+  }, [idx, selectIndex, updateOptions]);
 
   const inlineStyle = `
   td.code {
@@ -144,9 +108,7 @@ export function Root() {
       <div>
         <DiffOptionsControl
           options={options}
-          setOptions={setDiffOptions}
-          maxDiffWidth={maxDiffWidth}
-          setMaxDiffWidth={setMaxDiffWidth}
+          updateOptions={updateOptions}
           defaultMaxDiffWidth={GIT_CONFIG.webdiff.maxDiffWidth}
           isVisible={showOptions}
           setIsVisible={setShowOptions}
@@ -160,7 +122,9 @@ export function Root() {
         />
         <NormalizeJSONOption
           normalizeJSON={normalizeJSON}
-          setNormalizeJSON={setNormalizeJSON}
+          setNormalizeJSON={v => {
+            updateOptions({normalizeJSON: v});
+          }}
           filePair={filePair}
         />
         {showKeyboardHelp ? (
diff --git a/ts/__tests__/diff-options.test.ts b/ts/__tests__/diff-options.test.ts
index 33f8721..cd262f3 100644
--- a/ts/__tests__/diff-options.test.ts
+++ b/ts/__tests__/diff-options.test.ts
@@ -1,20 +1,22 @@
-import {decodeDiffOptions, encodeDiffOptions} from '../diff-options';
+import {flagsToGitDiffOptions, gitDiffOptionsToFlags} from '../diff-options';
 
 describe('encodeDiffOptions', () => {
   it('should encode no flags', () => {
-    expect(encodeDiffOptions({})).toEqual([]);
+    expect(gitDiffOptionsToFlags({})).toEqual([]);
   });
 
   it('should encode basic flags', () => {
-    expect(encodeDiffOptions({diffAlgorithm: 'patience'})).toEqual(['--diff-algorithm=patience']);
-    expect(encodeDiffOptions({ignoreAllSpace: true})).toEqual(['-w']);
-    expect(encodeDiffOptions({ignoreSpaceChange: true})).toEqual(['-b']);
-    expect(encodeDiffOptions({unified: 16})).toEqual(['-U16']);
-    expect(encodeDiffOptions({functionContext: true})).toEqual(['-W']);
+    expect(gitDiffOptionsToFlags({diffAlgorithm: 'patience'})).toEqual([
+      '--diff-algorithm=patience',
+    ]);
+    expect(gitDiffOptionsToFlags({ignoreAllSpace: true})).toEqual(['-w']);
+    expect(gitDiffOptionsToFlags({ignoreSpaceChange: true})).toEqual(['-b']);
+    expect(gitDiffOptionsToFlags({unified: 16})).toEqual(['-U16']);
+    expect(gitDiffOptionsToFlags({functionContext: true})).toEqual(['-W']);
   });
 
   it('should decode flags', () => {
-    expect(decodeDiffOptions(['-w'])).toEqual({ignoreAllSpace: true});
-    expect(decodeDiffOptions(['-W'])).toEqual({functionContext: true});
+    expect(flagsToGitDiffOptions(['-w'])).toEqual({ignoreAllSpace: true});
+    expect(flagsToGitDiffOptions(['-W'])).toEqual({functionContext: true});
   });
 });
diff --git a/ts/codediff/KeyboardShortcuts.tsx b/ts/codediff/KeyboardShortcuts.tsx
index 242d1c7..5a01f67 100644
--- a/ts/codediff/KeyboardShortcuts.tsx
+++ b/ts/codediff/KeyboardShortcuts.tsx
@@ -68,6 +68,9 @@ export function KeyboardShortcuts(props: KeyboardShortcutsProps) {
             <li>
               <kbd>v</kbd> Toggle file list / dropdown menu
             </li>
+            <li>
+              <kbd>z</kbd> Normalize JSON
+            </li>
             <li>
               <kbd>.</kbd> Show diff options
             </li>
diff --git a/ts/codediff/NormalizeJSONOption.tsx b/ts/codediff/NormalizeJSONOption.tsx
index 15cd780..8aea399 100644
--- a/ts/codediff/NormalizeJSONOption.tsx
+++ b/ts/codediff/NormalizeJSONOption.tsx
@@ -20,14 +20,14 @@ export function NormalizeJSONOption(props: NormalizeJSONOptionProps) {
   };
 
   return (
-    <>
+    <div className="diff-mode-controls">
       <input
         type="checkbox"
         checked={props.normalizeJSON}
         onChange={toggleNormalizeJSON}
         id="normalize-json"
       />{' '}
-      <label htmlFor="normalize-json">Normalize JSON (indent, sort keys)</label>
-    </>
+      <label htmlFor="normalize-json">Normalize JSON (z): indent, sort keys</label>
+    </div>
   );
 }
diff --git a/ts/codediff/codediff.tsx b/ts/codediff/codediff.tsx
index 71b4a2b..75ecb12 100644
--- a/ts/codediff/codediff.tsx
+++ b/ts/codediff/codediff.tsx
@@ -25,6 +25,13 @@ const DEFAULT_PARAMS: PatchOptions = {
   expandLines: 10,
 };
 
+/**
+ * Long lines can bog down the browser or freeze it completely.
+ * We show an interstitial before rendering diffs if the first line is more than
+ * this many characters.
+ */
+export const LINE_LENGTH_FOR_WARNING = 200_000;
+
 /**
  * @return Lines marked up with syntax <span>s. The <span>
  *     tags will be balanced within each line.
@@ -81,7 +88,20 @@ export function CodeDiff(props: Props) {
     return [highlightText(beforeText ?? '', language), highlightText(afterText ?? '', language)];
   }, [language, numLines, beforeText, afterText]);
 
-  return (
+  const [bypassSafetyCheck, setBypassSafetyCheck] = React.useState(false);
+
+  const isSafeToRender = React.useMemo(() => {
+    return (
+      Math.max(beforeLines[0]?.length ?? 0, afterLines[0]?.length ?? 0) < LINE_LENGTH_FOR_WARNING
+    );
+  }, [afterLines, beforeLines]);
+
+  // Make the user click the link again if they navigate to a new file.
+  React.useEffect(() => {
+    setBypassSafetyCheck(false);
+  }, [beforeText, afterText]);
+
+  return isSafeToRender || bypassSafetyCheck ? (
     <CodeDiffView
       beforeLines={beforeLines}
       beforeLinesHighlighted={beforeLinesHighlighted}
@@ -91,6 +111,26 @@ export function CodeDiff(props: Props) {
       params={fullParams}
       ops={diffRanges}
     />
+  ) : (
+    <div className="diff">
+      <table className="diff">
+        <tr>
+          <td className="code equal before suppressed-large-diff">
+            <p>⚠️ This file may be minified and the diff may slow down the browser. ⚠️</p>
+            <p>
+              <a
+                href="#"
+                onClick={e => {
+                  e.preventDefault();
+                  setBypassSafetyCheck(true);
+                }}>
+                Render diff anyway
+              </a>
+            </p>
+          </td>
+        </tr>
+      </table>
+    </div>
   );
 }
 
diff --git a/ts/diff-options.ts b/ts/diff-options.ts
index feafb18..fdf5595 100644
--- a/ts/diff-options.ts
+++ b/ts/diff-options.ts
@@ -1,6 +1,7 @@
 export type DiffAlgorithm = 'patience' | 'minimal' | 'histogram' | 'myers';
 
-export interface DiffOptions {
+/** Options that can be passed to `git diff --no-index` */
+export interface GitDiffOptions {
   /** aka -w */
   ignoreAllSpace: boolean;
   /** aka -b */
@@ -17,7 +18,7 @@ export interface DiffOptions {
   findCopies?: number;
 }
 
-export function encodeDiffOptions(opts: Partial<DiffOptions>) {
+export function gitDiffOptionsToFlags(opts: Partial<GitDiffOptions>) {
   const flags = [];
   if (opts.ignoreAllSpace) {
     flags.push('-w');
@@ -43,8 +44,8 @@ export function encodeDiffOptions(opts: Partial<DiffOptions>) {
   return flags;
 }
 
-export function decodeDiffOptions(flags: string[]): Partial<DiffOptions> {
-  const options: Partial<DiffOptions> = {};
+export function flagsToGitDiffOptions(flags: string[]): Partial<GitDiffOptions> {
+  const options: Partial<GitDiffOptions> = {};
   for (const flag of flags) {
     if (flag == '-w' || flag == '--ignore-all-space') {
       options.ignoreAllSpace = true;
diff --git a/ts/options.ts b/ts/options.ts
index e90c810..e1dcdb9 100644
--- a/ts/options.ts
+++ b/ts/options.ts
@@ -1,4 +1,9 @@
-import {DiffAlgorithm} from './diff-options';
+import {
+  DiffAlgorithm,
+  flagsToGitDiffOptions,
+  GitDiffOptions,
+  gitDiffOptionsToFlags,
+} from './diff-options';
 
 /** Type of global git_config object */
 export interface GitConfig {
@@ -48,3 +53,35 @@ export function injectStylesFromConfig() {
   </style>
   `);
 }
+
+export interface Options extends GitDiffOptions {
+  maxDiffWidth: number;
+  normalizeJSON: boolean;
+}
+
+export function parseOptions(query: URLSearchParams): Partial<Options> {
+  const flags = query.getAll('flag');
+  const gitDiffOptions = flagsToGitDiffOptions(flags);
+  const maxWidthStr = query.get('width');
+  const maxDiffWidth = maxWidthStr ? {maxDiffWidth: Number(maxWidthStr)} : undefined;
+  const normalizeJsonStr = query.get('normalize_json');
+  const normalizeJSON = normalizeJsonStr ? {normalizeJSON: true} : undefined;
+  return {...gitDiffOptions, ...maxDiffWidth, ...normalizeJSON};
+}
+
+export function encodeOptions(options: Partial<Options>) {
+  const {maxDiffWidth, normalizeJSON, ...diffOptions} = options;
+  const flags = gitDiffOptionsToFlags(diffOptions);
+  const params = new URLSearchParams(flags.map(f => ['flag', f]));
+  if (maxDiffWidth !== undefined && maxDiffWidth !== GIT_CONFIG.webdiff.maxDiffWidth) {
+    params.set('width', String(maxDiffWidth));
+  }
+  if (normalizeJSON) {
+    params.set('normalize_json', '1');
+  }
+  return params;
+}
+
+export type UpdateOptionsFn = (
+  updater: ((oldOptions: Partial<Options>) => Partial<Options>) | Partial<Options>,
+) => void;
diff --git a/ts/package.json b/ts/package.json
index ce73b97..91412fd 100644
--- a/ts/package.json
+++ b/ts/package.json
@@ -1,6 +1,6 @@
 {
   "name": "webdiff",
-  "version": "1.3.0",
+  "version": "1.3.0b2",
   "description": "client-side code for webdiff",
   "main": "index.js",
   "author": "Dan Vanderkam (danvdk@gmail.com)",
diff --git a/ts/utils.ts b/ts/utils.ts
index 0632239..10ac5b0 100644
--- a/ts/utils.ts
+++ b/ts/utils.ts
@@ -64,3 +64,8 @@ export function isSameSizeImagePair(filePair: FilePair) {
 export function assertUnreachable(x: never): never {
   throw new Error(x);
 }
+
+// See https://effectivetypescript.com/2020/05/12/unionize-objectify/
+export type Unionize<T extends object> = {
+  [k in keyof T]: {k: k; v: T[k]};
+}[keyof T];
diff --git a/webdiff/static/css/style.css b/webdiff/static/css/style.css
index 92a49f6..7bccd2e 100644
--- a/webdiff/static/css/style.css
+++ b/webdiff/static/css/style.css
@@ -106,29 +106,30 @@ ul.file-list {
 .side-a { border: 1px solid red; }
 .side-b { border: 1px solid green; }
 
-.image-diff-controls {
+/* Per-file type diff controls: image diff mode, JSON normalization */
+.diff-mode-controls {
   text-align: center;
   background-color: #f7f7f7;
   padding: 5px;
 }
-.image-diff-controls > input {
+.diff-mode-controls > input {
   margin-left: 20px;
 }
-.image-diff-controls a {
+.diff-mode-controls a {
   text-decoration: none;
 }
-.image-diff-controls a, .image-diff-controls a:visited {
+.diff-mode-controls a, .diff-mode-controls a:visited {
   color: #666;
 }
-.image-diff-controls b {
+.diff-mode-controls b {
   color: black;
 }
-.image-diff-controls .mode {
+.diff-mode-controls .mode {
   padding-left: 5px;
   padding-right: 5px;
   border-right: 1px solid #ccc;
 }
-.image-diff-controls .mode:last-child {
+.diff-mode-controls .mode:last-child {
   border-right: none;
 }
 
@@ -245,3 +246,8 @@ kbd {
   list-style-type: none;
   margin-bottom: 2px;
 }
+
+.suppressed-large-diff {
+  text-align: center;
+  background-color: lightyellow;
+}