Skip to content
https://json.org

Lighthouse Mobile

· 0 checks — Mobile Lighthouse audit -- Performance, Accessibility, Best Practices, and SEO category breakdown.
SCORE
0
GRADE
FIX
0
REVIEW
0
PASS
0
INFO
0

Detailed Report

Audit breakdown by category with detailed findings.

82

Performance

Insights

Remove large, duplicate JavaScript modules from bundles to reduce unnecessary bytes consumed by network activity.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Polyfills and transforms enable older browsers to use new JavaScript features. However, many aren't necessary for modern browsers. Consider modifying your JavaScript build process to not transpile Baseline features, unless you know you must support older browsers. Learn why most sites can deploy ES6+ code without transpiling

Why this matters

Performance issues directly impact user engagement and conversion rates.

3rd party code can significantly impact load performance. Reduce and defer loading of 3rd party code to prioritize your page's content.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Layout shifts occur when elements move absent any user interaction. Investigate the causes of layout shifts, such as elements being added, removed, or their fonts changing as the page loads.

Why this matters

Performance issues directly impact user engagement and conversion rates.

headings: [map[key:node label:Element subItemsHeading:map[key:extra] valueType:node] map[granularity:0.001 key:score label:Layout shift score subItemsHeading:map[key:cause valueType:text] valueType:numeric]]
items: [map[node:map[type:text value:Total] score:0.245165] map[node:map[boundingRect:map[bottom:3487 height:3205 left:628 right:923 top:282 width:295] lhId:page-9-DIV nodeLabel:json element value object array string number "true" "false" "null" object … path:1,HTML,1,BODY,6,DIV,1,DIV selector:body > div#spec > div#grammar snippet:<div id="grammar"> type:node] score:0.178139 subItems:map[items:[map[cause:Unsized image element extra:map[boundingRect:map[bottom:995 height:259 left:57 right:612 top:736 width:555] lhId:page-13-IMG nodeLabel:div#spec > div#text > center > img path:1,HTML,1,BODY,6,DIV,0,DIV,6,CENTER,0,IMG selector:div#spec > div#text > center > img snippet:<img src="https://www.json.org/img/object.png" style="width: 100%;"> type:node]] map[cause:Web font extra:map[type:url value:https://www.json.org/Programma-Bold.woff2]]] type:subitems]] map[node:map[boundingRect:map[bottom:3126 height:626 left:57 right:612 top:2500 width:555] lhId:page-8-CENTER nodeLabel:body > div#spec > div#text > center path:1,HTML,1,BODY,6,DIV,0,DIV,14,CENTER selector:body > div#spec > div#text > center snippet:<center> type:node] score:0.028174 subItems:map[items:[map[cause:Unsized image element extra:map[boundingRect:map[bottom:1677 height:391 left:57 right:612 top:1286 width:555] lhId:page-15-IMG nodeLabel:div#spec > div#text > center > img path:1,HTML,1,BODY,6,DIV,0,DIV,10,CENTER,0,IMG selector:div#spec > div#text > center > img snippet:<img src="https://www.json.org/img/value.png" style="width: 100%;"> type:node]]] type:subitems]] map[node:map[boundingRect:map[bottom:1752 height:54 left:57 right:612 top:1698 width:555] lhId:page-1-P nodeLabel:A string is a sequence of zero or more Unicode characters, wrapped in double qu… path:1,HTML,1,BODY,6,DIV,0,DIV,11,P selector:body > div#spec > div#text > p snippet:<p> type:node] score:0.015318 subItems:map[items:[map[cause:Unsized image element extra:map[boundingRect:map[bottom:995 height:259 left:57 right:612 top:736 width:555] lhId:page-13-IMG nodeLabel:div#spec > div#text > center > img path:1,HTML,1,BODY,6,DIV,0,DIV,6,CENTER,0,IMG selector:div#spec > div#text > center > img snippet:<img src="https://www.json.org/img/object.png" style="width: 100%;"> type:node]]] type:subitems]] map[node:map[boundingRect:map[bottom:3126 height:626 left:57 right:612 top:2500 width:555] lhId:page-8-CENTER nodeLabel:body > div#spec > div#text > center path:1,HTML,1,BODY,6,DIV,0,DIV,14,CENTER selector:body > div#spec > div#text > center snippet:<center> type:node] score:0.013022 subItems:map[items:[map[cause:Unsized image element extra:map[boundingRect:map[bottom:2427 height:659 left:57 right:612 top:1768 width:555] lhId:page-16-IMG nodeLabel:div#spec > div#text > center > img path:1,HTML,1,BODY,6,DIV,0,DIV,12,CENTER,0,IMG selector:div#spec > div#text > center > img snippet:<img src="https://www.json.org/img/string.png" style="width: 100%;"> type:node]]] type:subitems]] map[node:map[boundingRect:map[bottom:2432 height:664 left:57 right:612 top:1768 width:555] lhId:page-6-CENTER nodeLabel:body > div#spec > div#text > center path:1,HTML,1,BODY,6,DIV,0,DIV,12,CENTER selector:body > div#spec > div#text > center snippet:<center> type:node] score:0.006293 subItems:map[items:[map[cause:Unsized image element extra:map[boundingRect:map[bottom:1213 height:145 left:57 right:612 top:1068 width:555] lhId:page-14-IMG nodeLabel:div#spec > div#text > center > img path:1,HTML,1,BODY,6,DIV,0,DIV,8,CENTER,0,IMG selector:div#spec > div#text > center > img snippet:<img src="https://www.json.org/img/array.png" style="width: 100%;"> type:node]]] type:subitems]]]

Consider setting font-display to swap or optional to ensure text is consistently visible. swap can be further optimized to mitigate layout shifts with font metric overrides.

Why this matters

Performance issues directly impact user engagement and conversion rates.

URLEst Savings
www.json.org/Programma-Bold.woff2395 ms

Optimize LCP by making the LCP image discoverable from the HTML immediately, and avoiding lazy-loading

Why this matters

Performance issues directly impact user engagement and conversion rates.

lhId: page-0-IMG
nodeLabel: div#spec > div#text > center > img
path: 1,HTML,1,BODY,6,DIV,0,DIV,14,CENTER,0,IMG
selector: div#spec > div#text > center > img
snippet: <img src="https://www.json.org/img/number.png" style="width: 100%;">

Avoid chaining critical requests by reducing the length of chains, reducing the download size of resources, or deferring the download of unnecessary resources to improve page load.

Why this matters

Performance issues directly impact user engagement and conversion rates.

description: [preconnect](https://developer.chrome.com/docs/lighthouse/performance/uses-rel-preconnect/) hints help the browser establish a connection earlier in the page load, saving time when the first request for that origin is made. The following are the origins that the page preconnected to.
title: Preconnected origins
value: no origins were preconnected
description: Add [preconnect](https://developer.chrome.com/docs/lighthouse/performance/uses-rel-preconnect/) hints to your most important origins, but try to use no more than 4.
title: Preconnect candidates
value: No additional origins are good candidates for preconnecting

A long cache lifetime can speed up repeat visits to your page. Learn more about caching.

Why this matters

Performance issues directly impact user engagement and conversion rates.

RequestCache TTLTransfer Size
www.json.org/img/string.png0.0 ms49.3 KiB
www.json.org/img/number.png0.0 ms36.4 KiB
www.json.org/Programma-Bold.woff20.0 ms33.7 KiB
www.json.org/img/value.png0.0 ms23.6 KiB
www.json.org/img/object.png0.0 ms19.8 KiB
www.json.org/img/whitespace.png0.0 ms18.3 KiB
www.json.org/img/json160.gif0.0 ms11.9 KiB
www.json.org/img/array.png0.0 ms11.4 KiB

Reducing the download time of images can improve the perceived load time of the page and LCP. Learn more about optimizing image size

Why this matters

Performance issues directly impact user engagement and conversion rates.

URLResource SizeEst Savings
div#spec > div#text > center > img div#spec > div#text > center > img
www.json.org/img/string.png49.0 KiB35.3 KiB
div#spec > div#text > center > img div#spec > div#text > center > img
www.json.org/img/number.png36.1 KiB26.0 KiB
div#spec > div#text > center > img div#spec > div#text > center > img
www.json.org/img/value.png23.3 KiB16.8 KiB
div#spec > div#text > center > img div#spec > div#text > center > img
www.json.org/img/object.png19.6 KiB14.1 KiB
div#spec > div#text > center > img div#spec > div#text > center > img
www.json.org/img/whitespace.png18.1 KiB13.0 KiB
div#spec > div#text > center > img div#spec > div#text > center > img
www.json.org/img/array.png11.2 KiB8.1 KiB

Tap interactions may be delayed by up to 300 ms if the viewport is not optimized for mobile.

Why this matters

Performance issues directly impact user engagement and conversion rates.

These insights are also available in the Chrome DevTools Performance Panel - record a trace to view more detailed information.

Diagnostics

Set an explicit width and height on image elements to reduce layout shifts and improve CLS. Learn how to set image dimensions

Why this matters

Performance issues directly impact user engagement and conversion rates.

URL
div#spec > div#text > center > img div#spec > div#text > center > img
www.json.org/img/string.png
div#spec > div#text > center > img div#spec > div#text > center > img
www.json.org/img/number.png
div#spec > div#text > center > img div#spec > div#text > center > img
www.json.org/img/value.png
div#spec > div#text > center > img div#spec > div#text > center > img
www.json.org/img/whitespace.png
div#spec > div#text > center > img div#spec > div#text > center > img
www.json.org/img/object.png
div#spec > div#text > center > img div#spec > div#text > center > img
www.json.org/img/array.png

More information about the performance of your application. These numbers don't directly affect the Performance score.

Redirects introduce additional delays before the page can be loaded. Learn how to avoid page redirects.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Estimated savings: 1.2 s
URLTime Spent
json.org/1.2 s
www.json.org/json-en.html0.0 ms

These are the largest layout shifts observed on the page. Each table item represents a single layout shift, and shows the element that shifted the most. Below each item are possible root causes that led to the layout shift. Some of these layout shifts may not be included in the CLS metric value due to windowing. Learn how to improve CLS

Why this matters

Performance issues directly impact user engagement and conversion rates.

ElementLayout shift score
json element value object array string number "true" "false" "null" object … body > div#spec > div#grammar
0.178
body > div#spec > div#text > center body > div#spec > div#text > center
0.028
A string is a sequence of zero or more Unicode characters, wrapped in double qu… body > div#spec > div#text > p
0.015
body > div#spec > div#text > center body > div#spec > div#text > center
0.013
body > div#spec > div#text > center body > div#spec > div#text > center
0.006
Whitespace can be inserted between any pair of tokens. Excepting a few encoding… body > div#spec > div#text > p
0.004
●Time to Interactive 2.6 s
●Document request latency
●Optimize DOM size
●Forced reflow
●LCP breakdown
●Modern HTTP
●Render blocking requests
●Max Potential First Input Delay 20 ms
●Minify CSS
●Minify JavaScript
●Reduce unused CSS
●Reduce unused JavaScript
●Avoids enormous network payloads Total size was 243 KiB
●JavaScript execution time 0.0 s
●Minimizes main-thread work 0.4 s
●Avoid long main-thread tasks 1 long task found
●Page didn't prevent back/forward cache restoration
●Network Requests
●Network Round Trip Times 130 ms
●Server Backend Latencies 260 ms
●Tasks
●Diagnostics
●Metrics
●Screenshot Thumbnails
●Final Screenshot
●Script Treemap Data
●Resources Summary
●Initial server response time was short Root document took 270 ms
○INP breakdown
○User Timing marks and measures
○Avoid non-composited animations
67

Accessibility

These checks highlight opportunities to improve the accessibility of your web app. Automatic detection can only detect a subset of issues and does not guarantee the accessibility of your web app, so manual testing is also encouraged.

Internationalization and localization

If a page doesn't specify a `lang` attribute, a screen reader assumes that the page is in the default language that the user chose when setting up the screen reader. If the page isn't actually in the default language, then the screen reader might not announce the page's text correctly. Learn more about the `lang` attribute.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failing Elements
html html

These are opportunities to improve the interpretation of your content by users in different locales.

Names and labels

Informative elements should aim for short, descriptive alternate text. Decorative elements can be ignored with an empty alt attribute. Learn more about the `alt` attribute.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failing Elements
div#spec > div#text > center > img div#spec > div#text > center > img
div#spec > div#text > center > img div#spec > div#text > center > img
div#spec > div#text > center > img div#spec > div#text > center > img
div#spec > div#text > center > img div#spec > div#text > center > img
div#spec > div#text > center > img div#spec > div#text > center > img
div#spec > div#text > center > img div#spec > div#text > center > img

These are opportunities to improve the semantics of the controls in your application. This may enhance the experience for users of assistive technology, like a screen reader.

Best practices

Touch targets with sufficient size and spacing help users who may have difficulty targeting small controls to activate the targets. Learn more about touch targets.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failing Elements
العربية body > div > small > a
Български body > div > small > a
中文 body > div > small > a
Český body > div > small > a
Dansk body > div > small > a
Nederlands body > div > small > a
Esperanto body > div > small > a
Deutsch body > div > small > a
Ελληνικά body > div > small > a
עברית body > div > small > a
Magyar body > div > small > a
Indonesia body > div > small > a
Italiano body > div > small > a
日本 body > div > small > a
한국어 body > div > small > a
Norsk body > div > small > a
Polski body > div > small > a
Português body > div > small > a
Română body > div > small > a
Српско-хрватски body > div > small > a
Slovenščina body > div > small > a
Español body > div > small > a
Svenska body > div > small > a
Türkçe body > div > small > a
Українська body > div > small > a
Tiếng Việt body > div > small > a
JSON for ASP li > ul > li > a
JSON ASP utility class li > ul > li > a
JSON.awk li > ul > li > a
rhawk li > ul > li > a
mu_json li > ul > li > a
JSON_checker li > ul > li > a
YAJL li > ul > li > a
LibU li > ul > li > a
json-c li > ul > li > a
json-parser li > ul > li > a
jsonsl li > ul > li > a
WJElement li > ul > li > a
M's JSON parser li > ul > li > a
cJSON li > ul > li > a
Jansson li > ul > li > a
jsmn li > ul > li > a
parson li > ul > li > a
ujson4c li > ul > li > a
frozen li > ul > li > a
microjson li > ul > li > a
mjson li > ul > li > a
progbase li > ul > li > a
lwjson li > ul > li > a
cisson li > ul > li > a
nanoJSONc li > ul > li > a
JSON-BUILD li > ul > li > a
JSONKit li > ul > li > a
jsonme-- li > ul > li > a
ThorsSerializer li > ul > li > a
JsonBox li > ul > li > a
jvar li > ul > li > a
rapidjson li > ul > li > a
minijson li > ul > li > a
jsoncons li > ul > li > a
jsoncpp li > ul > li > a
univalue li > ul > li > a
jsovon li > ul > li > a
ArduinoJson li > ul > li > a
QJson li > ul > li > a
CAJUN li > ul > li > a
libjson li > ul > li > a
nosjob li > ul > li > a
qmjson li > ul > li > a
JSON Support in Qt li > ul > li > a
JsonWax for Qt li > ul > li > a
progbase li > ul > li > a
Qentem-Engine li > ul > li > a
fastJSON li > ul > li > a
JSON_checker li > ul > li > a
Json.NET li > ul > li > a
JSON for .NET li > ul > li > a
Manatee Json li > ul > li > a
FastJsonParser li > ul > li > a
LightJson li > ul > li > a
Liersch.Json li > ul > li > a
Liersch.JsonSerialization li > ul > li > a
progbase li > ul > li > a
JSON Essentials li > ul > li > a
std.json li > ul > li > a
asdf li > ul > li > a
Delphi Web Utils li > ul > li > a
JSON Delphi Library li > ul > li > a
json-fortran li > ul > li > a
YAJL-Fort li > ul > li > a
jsonff li > ul > li > a
RJson package li > ul > li > a
json package li > ul > li > a
JSON-java li > ul > li > a
esson li > ul > li > a
JSONUtil li > ul > li > a
jsonp li > ul > li > a
Json-lib li > ul > li > a
Stringtree li > ul > li > a
SOJO li > ul > li > a
json-taglib li > ul > li > a
Flexjson li > ul > li > a
Argo li > ul > li > a
jsonij li > ul > li > a
fastjson li > ul > li > a
mjson li > ul > li > a
jjson li > ul > li > a
json-simple li > ul > li > a
json-io li > ul > li > a
google-gson li > ul > li > a
FOSS Nova JSON li > ul > li > a
Corn CONVERTER li > ul > li > a
Apache johnzon li > ul > li > a
Genson li > ul > li > a
cookjson li > ul > li > a
progbase li > ul > li > a
jackson li > ul > li > a
MOXy li > ul > li > a
JSON li > ul > li > a
json2.js li > ul > li > a
clarinet li > ul > li > a
Oboe.js li > ul > li > a
progbase li > ul > li > a
JSONlab li > ul > li > a
20565 li > ul > li > a
23393 li > ul > li > a
NSJSONSerialization li > ul > li > a
json-framework li > ul > li > a
JSONKit li > ul > li > a
yajl-objc li > ul > li > a
TouchJSON li > ul > li > a
Public.Parser.JSON li > ul > li > a
Public.Parser.JSON2 li > ul > li > a
simplejson li > ul > li > a
pyson li > ul > li > a
Yajl-Py li > ul > li > a
ultrajson li > ul > li > a
metamagic.json li > ul > li > a
progbase li > ul > li > a
rjson li > ul > li > a
jsonlite li > ul > li > a
Serde JSON li > ul > li > a
json-rust li > ul > li > a
yajl-ruby li > ul > li > a
json-stream li > ul > li > a
progbase li > ul > li > a
MZScheme li > ul > li > a
JSON-struct li > ul > li > a
Jshon li > ul > li > a
JSON.sh li > ul > li > a
jwalk li > ul > li > a
VB-JSON li > ul > li > a
PW.JSON li > ul > li > a
progbase li > ul > li > a
fwJSON li > ul > li > a
JSON li > ul > li > a
vfpjson li > ul > li > a
Videos about JSON div > ul > li > a
Videos about the JSON Logo div > ul > li > a
Heresy & Heretical Open Source: A Heretic's Perspective div > ul > li > a
Nota Message Format div > ul > li > a

One main landmark helps screen reader users navigate a web page. Learn more about landmarks.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failing Elements
html html

These items highlight common accessibility best practices.

○Interactive controls are keyboard focusable
○Interactive elements indicate their purpose and state
○The page has a logical tab order
○Visual order on the page follows DOM order
○User focus is not accidentally trapped in a region
○The user's focus is directed to new content added to the page
○HTML5 landmark elements are used to improve navigation
○Offscreen content is hidden from assistive technology
○Custom controls have associated labels
○Custom controls have ARIA roles
●`[aria-hidden="true"]` is not present on the document `<body>`
●Background and foreground colors have a sufficient contrast ratio
●Document has a `<title>` element
●Links have a discernible name
●Lists contain only `<li>` elements and script supporting elements (`<script>` and `<template>`).
●List items (`<li>`) are contained within `<ul>`, `<ol>` or `<menu>` parent elements
●Cells in a `<table>` element that use the `[headers]` attribute refer to table cells within the same table.
●Heading elements appear in a sequentially-descending order
●Identical links have the same purpose.
○`[accesskey]` values are unique
○`[aria-*]` attributes match their roles
○`button`, `link`, and `menuitem` elements have accessible names
○ARIA attributes are used as specified for the element's role
○Deprecated ARIA roles were not used
○Elements with `role="dialog"` or `role="alertdialog"` have accessible names.
○`[aria-hidden="true"]` elements do not contain focusable descendents
○ARIA input fields have accessible names
○ARIA `meter` elements have accessible names
○ARIA `progressbar` elements have accessible names
○Elements use only permitted ARIA attributes
○`[role]`s have all required `[aria-*]` attributes
○Elements with an ARIA `[role]` that require children to contain a specific `[role]` have all required children.
○`[role]`s are contained by their required parent element
○`[role]` values are valid
○Elements with the `role=text` attribute do not have focusable descendents.
○ARIA toggle fields have accessible names
○ARIA `tooltip` elements have accessible names
○ARIA `treeitem` elements have accessible names
○`[aria-*]` attributes have valid values
○`[aria-*]` attributes are valid and not misspelled
○Buttons have an accessible name
○The page contains a heading, skip link, or landmark region
○`<dl>`'s contain only properly-ordered `<dt>` and `<dd>` groups, `<script>`, `<template>` or `<div>` elements.
○Definition list items are wrapped in `<dl>` elements
○ARIA IDs are unique
○No form fields have multiple labels
○`<frame>` or `<iframe>` elements have a title
○`<html>` element has a valid value for its `[lang]` attribute
○`<html>` element has an `[xml:lang]` attribute with the same base language as the `[lang]` attribute.
○Input buttons have discernible text.
○`<input type="image">` elements have `[alt]` text
○Form elements have associated labels
○Links are distinguishable without relying on color.
○The document does not use `<meta http-equiv="refresh">`
○`[user-scalable="no"]` is not used in the `<meta name="viewport">` element and the `[maximum-scale]` attribute is not less than 5.
○`<object>` elements have alternate text
○Select elements have associated label elements.
○Skip links are focusable.
○No element has a `[tabindex]` value greater than 0
○`<th>` elements and elements with `[role="columnheader"/"rowheader"]` have data cells they describe.
○`[lang]` attributes have a valid value
○`<video>` elements contain a `<track>` element with `[kind="captions"]`
○Tables have different content in the summary attribute and `<caption>`.
○All heading elements contain content.
○Uses ARIA roles only on compatible elements
○Image elements do not have `[alt]` attributes that are redundant text.
○Elements with visible text labels have matching accessible names.
○Tables use `<caption>` instead of cells with the `[colspan]` attribute to indicate a caption.
○`<td>` elements in a large `<table>` have one or more table headers.
96

Best Practices

User Experience

Image natural dimensions should be proportional to the display size and the pixel ratio to maximize image clarity. Learn how to provide responsive images.

Why this matters

Performance issues directly impact user engagement and conversion rates.

URLDisplayed sizeActual sizeExpected size
json logo tbody > tr > td > img
www.json.org/img/json160.gif160 x 160160 x 160240 x 240
●Uses HTTPS
●Avoids deprecated APIs
●Avoids third-party cookies
●Allows users to paste into input fields
●Avoids requesting the geolocation permission on page load
●Avoids requesting the notification permission on page load
●Displays images with correct aspect ratio
●Page has the HTML doctype
●Properly defines charset
●No browser errors logged to the console
●No issues in the `Issues` panel in Chrome Devtools
●Ensure CSP is effective against XSS attacks
●Use a strong HSTS policy
●Ensure proper origin isolation with COOP
●Mitigate clickjacking with XFO or CSP
●Mitigate DOM-based XSS with Trusted Types
●Page has valid source maps
○Redirects HTTP traffic to HTTPS
○Detected JavaScript libraries
82

SEO

These checks ensure that your page is following basic search engine optimization advice. There are many additional factors Lighthouse does not score here that may affect your search ranking, including performance on Core Web Vitals. Learn more about Google Search Essentials.

Content Best Practices

Meta descriptions may be included in search results to concisely summarize page content. Learn more about the meta description.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Informative elements should aim for short, descriptive alternate text. Decorative elements can be ignored with an empty alt attribute. Learn more about the `alt` attribute.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failing Elements
div#spec > div#text > center > img div#spec > div#text > center > img
div#spec > div#text > center > img div#spec > div#text > center > img
div#spec > div#text > center > img div#spec > div#text > center > img
div#spec > div#text > center > img div#spec > div#text > center > img
div#spec > div#text > center > img div#spec > div#text > center > img
div#spec > div#text > center > img div#spec > div#text > center > img

Format your HTML in a way that enables crawlers to better understand your app’s content.

○Structured data is valid
●Page isn’t blocked from indexing
●Document has a `<title>` element
●Page has successful HTTP status code
●Links have descriptive text
●Links are crawlable
●Document has a valid `hreflang`
○robots.txt is valid
○Document has a valid `rel=canonical`

Send Feedback