Front-End Checklist

The Front-End Checklist is an exhaustive list of all elements you need to have / to test before launching your site / page HTML to production.

It is based on Front-End developers' years of experience, with the additions coming from some other open-source checklists.

How to use?

All items in the Front-End Checklist are required for the majority of the projects, but some elements can be omitted or are not essential (in the case of an administration web app, you may not need RSS feed for example). We choose to use 3 levels of flexibility:

means that the item is recommended but can be omitted in some particular situations.
means that the item is highly recommended and can eventually be omitted in some really particular cases. Some elements, if omitted, can have bad repercussions in terms of performance or SEO.
means that the item can't be omitted by any reason. You may cause a dysfunction in your page or have accessibility or SEO issues. The testing priority needs to be on these elements first.

Some resources possess an emoticon to help you understand which type of content / help you may find on the checklist:

📖: documentation or article
🛠: online tool / testing tool
📹: media or video content

Head

Notes: You can find a list of everything that could be found in the <head> of an HTML document.

Meta tag

Doctype: The Doctype is HTML5 and is at the top of all your HTML pages.

<!-- Doctype HTML5 -->
<!doctype html>

📖 Determining the character encoding - HTML5 W3C

The next 3 meta tags (Charset, X-UA Compatible and Viewport) need to come first in the head.

Charset: The charset declared (UTF-8) is declared correctly.

<!-- Set character encoding for the document -->
<meta charset="utf-8">

X-UA-Compatible: The X-UA-Compatible meta tag is present.

<!-- Instruct Internet Explorer to use its latest rendering engine -->
<meta http-equiv="x-ua-compatible" content="ie=edge">

📖 Specifying legacy document modes (Internet Explorer)

Viewport: The viewport is declared correctly.

<!-- Viewport for responsive web design -->
<meta name="viewport" content="width=device-width, initial-scale=1">

Title: A title is used on all pages (SEO: No more than 65 characters, website title included).

<!-- Document Title -->
<title>Page Title less than 65 characters</title>

📖 Title - HTML - MDN

Description: A meta description is provided, it is unique and doesn't possess more than 150 characters.

<!-- Meta Description -->
<meta name="description" content="Description of the page less than 150 characters">

Favicons: Each favicon has been created and displays correctly. If you have only a favicon.ico, put it at the root of your site. Normally you won't need to use any markup. However, it's still good practice to link to it using the example below. Today, PNG format is recommended over .ico format (dimensions: 32x32px).

<!-- Standard favicon -->
<link rel="icon" type="image/x-icon" href="https://example.com/favicon.ico">
<!-- Recommended favicon format -->
<link rel="icon" type="image/png" href="https://example.com/favicon.png">

🛠 Favicon Generator

🛠 RealFaviconGenerator

📖 Favicon Cheat Sheet

📖 Favicons, Touch Icons, Tile Icons, etc. Which Do You Need? - CSS Tricks

📖 PNG favicons - caniuse

Apple Touch Icon: Apple touch favicon apple-mobile-web-app-capable are present. (Create your Apple Icon file with at least 200x200px dimension to support all dimensions that you may need)

<!-- Apple Touch Icon -->
<link rel="apple-touch-icon" href="/custom-icon.png">

📖 Configuring Web Applications

Windows Tiles: Windows tiles are present and linked.

<!-- Microsoft Tiles -->
<meta name="msapplication-config" content="browserconfig.xml" />

Minimum required xml markup for the browserconfig.xml file is as follows:

<?xml version="1.0" encoding="utf-8"?>
<browserconfig>
   <msapplication>
     <tile>
        <square70x70logo src="small.png"/>
        <square150x150logo src="medium.png"/>
        <wide310x150logo src="wide.png"/>
        <square310x310logo src="large.png"/>
     </tile>
   </msapplication>
</browserconfig>

📖 Browser configuration schema reference

Canonical: Use rel="canonical" to avoid duplicate content.

<!-- Helps prevent duplicate content issues -->
<link rel="canonical" href="http://example.com/2017/09/a-new-article-to-red.html">

HTML tags

Language tag: The language tag of your website is specified and related to the language of the current page.

<html lang="en">

Direction tag: The direction of lecture is specified on the body tag (It can be used on another HTML tag).

<html dir="rtl">

📖 dir - HTML - MDN

Alternate language: The language tag of your website is specified and related to the language of the current page.

<link rel="alternate" href="https://es.example.com/" hreflang="es">

Conditional comments: Conditional comments are present for IE if needed.

📖 About conditional comments (Internet Explorer) - MSDN - Microsoft

RSS feed: If your project is a blog or has articles, an RSS link was provided.
CSS Critical: The CSS critical (or "above the fold") collects all the CSS used to render the visible portion of the page. It is embedded before your principal CSS call and between <style></style> in a single line (minified).

🛠 Critical by Addy Osmani on Github

CSS order: All CSS files are loaded before any JavaScript files in the <head>. (Except the case where sometimes JS files are loaded asynchronously on top of your page).

Social meta

Facebook OG and Twitter Cards are, for any website, highly recommended. The other social media tags can be considered if you target a particular presence on those and want to ensure the display.

Facebook Open Graph: All Facebook Open Graph (OG) are tested and no one is missing or with a false information. Images need to be at least 600 x 315 pixels, 1200 x 630 pixels recommended.

<meta property="og:type" content="website">
<meta property="og:url" content="https://example.com/page.html">
<meta property="og:title" content="Content Title">
<meta property="og:image" content="https://example.com/image.jpg">
<meta property="og:description" content="Description Here">
<meta property="og:site_name" content="Site Name">
<meta property="og:locale" content="en_US">

📖 A Guide to Sharing for Webmasters

🛠 Test your page with the Facebook OG testing

Twitter Card:

<meta name="twitter:card" content="summary">
<meta name="twitter:site" content="@site_account">
<meta name="twitter:creator" content="@individual_account">
<meta name="twitter:url" content="https://example.com/page.html">
<meta name="twitter:title" content="Content Title">
<meta name="twitter:description" content="Content description less than 200 characters">
<meta name="twitter:image" content="https://example.com/image.jpg">

📖 Getting started with cards — Twitter Developers

🛠 Test your page with the Twitter card validator

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HTML

Best practices

HTML5 Semantic Elements: HTML5 Semantic Elements are used appropriately (header, section, footer, main...).

📖 HTML Reference

Error pages: Error 404 page and 5xx exist. Remember that the 5xx error page needs to have his CSS integrated (no external call on the current server).
Noopener: In case you are using external links with target="_blank", your link should have a rel="noopener" attribute to prevent tab nabbing. If you need to support older versions of Firefox, use rel="noopener noreferrer".

📖 About rel=noopener

Clean up comments: Unnecessary code needs to be removed before sending the page to production.

HTML testing

W3C compliant: All pages need to be tested with the W3C validator to identify possible issues in the HTML code.

🛠 W3C validator

HTML Lint: I use tools to help me analyze any issues I could have on my HTML code.

🛠 Dirty markup

Desktop Browsers: All pages were tested on all current desktop browsers (Safari, Firefox, Chrome, Internet Explorer, EDGE...).
Mobile Browsers: All pages were tested on all current mobile browsers (Native browser, Chrome, Safari...).
Link checker: There are no broken links in my page, verify that you don't have any 404 error.

🛠 W3C Link Checker

Adblockers test: Your website shows your content correctly with adblockers enabled (You can provide a message encouraging people to disable their adblocker).

Pixel perfect: Pages are close to pixel perfect. Depending on the quality of the creatives, you may not be 100% accurate, but your page needs to be close to your template.

Pixel Perfect - Chrome Extension

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Webfonts

Webfont format: WOFF, WOFF2 and TTF are supported by all modern browsers.

📖 WOFF - Web Open Font Format - Caniuse.

📖 WOFF 2.0 - Web Open Font Format - Caniuse.

📖 TTF/OTF - TrueType and OpenType font support

📖 Using @font-face - CSS-Tricks

Webfont size: Webfont sizes don't exceed 2 MB (all variants included).

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CSS

Notes: Take a look at CSS guidelines and Sass Guidelines followed by most Front-End developers. If you have a doubt about CSS properties, you can visit CSS Reference.

Responsive Web Design: The website is using responsive web design.
CSS Print: A print stylesheet is provided and is correct on each page.
Preprocessors: Your page is using a CSS preprocessor (Sass is preferred).
Unique ID: If IDs are used, they are unique to a page.
Reset CSS: A CSS reset (reset, normalize or reboot) is used and up to date. (If you are using a CSS Framework like Bootstrap or Foundation, a Normalize is already included into it.)

📖 Reset.css

📖 Normalize.css

📖 Reboot

JS prefix: All classes (or id- used in JavaScript files) begin with js- and are not styled into the CSS files.

<div id="js-slider" class="my-slider">
<!-- Or -->
<div id="id-used-by-cms" class="js-slider my-slider">

CSS embed or line: Avoid at all cost the use of CSS embed or inline: only used for valid reasons (ex: background-image for slider, CSS critical).
Vendor prefixes: CSS vendor prefixes are used and are generated accordingly with your browser support compatibility.

🛠 Autoprefixer CSS online

Performance

Concatenation: CSS files are concatenated in a single file. (Not for HTTP/2)
Minification: All CSS files are minified.
Non-blocking: CSS files need to be non-blocking to prevent the DOM from taking time to load.

📖 loadCSS by filament group

📖 Example of preload CSS using loadCSS

Unused CSS: Remove unused CSS.

🛠 UnCSS Online 🛠

🛠 PurifyCSS

🛠 Chrome DevTools Coverage

CSS testing

Stylelint: All CSS or SCSS files are without any errors.

🛠 stylelint, a CSS linter

📖 Sass guidelines

Responsive web design: All pages were tested at the following breakpoints: 320px, 768px, 1024px (can be more / different according to your analytics).
CSS Validator: The CSS was tested and pertinent errors were corrected.

🛠 CSS Validator

Reading direction: All pages need to be tested for LTR and RTL languages if they need to be supported.

📖 Building RTL-Aware Web Apps & Websites: Part 1 - Mozilla Hacks

📖 Building RTL-Aware Web Apps & Websites: Part 2 - Mozilla Hacks

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Images

Notes: For a complete understanding of image optimization, check the free ebook Essential Image Optimization from Addy Osmani.

Best practices

Optimization: All images are optimized to be rendered in the browser. WebP format could be used for critical pages (like Homepage).

🛠 Imagemin

🛠 Use ImageOptim to optimise your images for free.

Retina: You provide layout images x2 or 3x, support retina display.
Sprite: Small images are in a sprite file (in the case of icons, they can be in an SVG sprite image).
Width and Height: All <img> have height and width set (Don't specify px or %).

Note: Lots of developers assume that width and height are not compatible with responsive web design. It's absolutely not the case.

Alternative text: All <img> have an alternative text which describe the image visually.
Lazy loading: Images are lazyloaded (A noscript fallback is always provided).

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JavaScript

Best practices

JavaScript Inline: You don't have any JavaScript code inline (mixed with your HTML code).
Concatenation: JavaScript files are concatenated.
Minification: JavaScript files are minified (you can add the .min suffix).

Minify Resources (HTML, CSS, and JavaScript)

JavaScript security:

Guidelines for Developing Secure Applications Utilizing JavaScript*

Non-blocking: JavaScript files are loaded asynchronously using async or deferred using defer attribute.

📖 Remove Render-Blocking JavaScript

Modernizr: If you need to target some specific features you can use a custom Modernizr to add classes in your <html> tag.

🛠 Customize your Modernizr

JavaScript testing

ESLint: No errors are flagged by ESLint (based on your configuration or standards rules).

📖 ESLint - The pluggable linting utility for JavaScript and JSX

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Security

Scan and check your web site

securityheaders.io

Observatory by Mozilla

ASafaWeb - Automated Security Analyser for ASP.NET Websites

Best practices

HTTPS: HTTPS is used on every pages and for all external content (plugins, images...).

🛠 Let's Encrypt - Free SSL/TLS Certificates

🛠 Free SSL Server Test

📖 Strict Transport Security

HTTP Strict Transport Security (HSTS): The HTTP header is set to 'Strict-Transport-Security'.

🛠 Check HSTS preload status and eligibility

📖 HTTP Strict Transport Security Cheat Sheet - OWASP

📖 Transport Layer Protection Cheat Sheet - OWASP

Cross Site Request Forgery (CSRF): You are ensure that requests made to your server-side are legitimate and originate from your website / app to prevent CSRF attacks.

📖 Cross-Site Request Forgery (CSRF) Prevention Cheat Sheet - OWASP

Cross Site Scripting (XSS): Your page or website is free from XSS possible issues.

📖 XSS (Cross Site Scripting) Prevention Cheat Sheet - OWASP

📖 DOM based XSS Prevention Cheat Sheet - OWASP

Content Type Options Prevents Google Chrome and Internet Explorer from trying to mime-sniff the content-type of a response away from the one being declared by the server.

📖 X-Content-Type-Options - Scott Helme

X-Frame-Options (XFO) Protects your visitors against clickjacking attacks.

📖 X-Frame-Options - Scott Helme

📖 RFC7034 - HTTP Header Field X-Frame-Options

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Performance

Best practices

Weight page: The weight of each page is between 0 and 500 KB.

🛠 Website Page Analysis

📖 Size Limit: Make the Web lighter

Minified: Your HTML is minified.

🛠 W3C Validator

Lazy loading: Images, scripts and CSS need to be lazy loaded to improve the response time of the current page (See details in their respective sections).
Cookie size: If you are using cookies be sure each cookie doesn't exceed 4096 bytes and your domain name doesn't have more than 20 cookies.

📖 Cookie specification: RFC 6265

📖 Cookies

🛠 Browser Cookie Limits

Preparing upcoming requests

📖 Explanation of the following techniques

DNS resolution: DNS of third-party services that may be needed are resolved in advance during idle time using dns-prefetch.

<link rel="dns-prefetch" href="https://example.com">

Preconnection: DNS lookup, TCP handshake and TLS negociation with services that will be needed soon is done in advance during idle time using preconnect.

<link rel="preconnect" href="https://example.com">

Prefetching: Resources that will be needed soon (e.g. lazy loaded images) are requested in advance during idle time using prefetch.

<link rel="prefetch" href="image.png">

Preloading: Resources needed in the current page (e.g. scripts placed at the end of <body>) in advance using preload.

<link rel="preload" href="app.js">

📖 Difference between prefetch and preload

Performance testing

Google PageSpeed: All your pages were tested (not only the homepage) and have a score of at least 90/100.

🛠 Google PageSpeed

🛠 Test your mobile speed with Google

🛠 WebPagetest - Website Performance and Optimization Test

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Accessibility

Notes: You can watch the playlist A11ycasts with Rob Dodson 📹

Best practices

Progressive enhancement: Major functionality like main navigation and search should work without JavaScript enabled.

📖 Enable / Disable JavaScript in Chrome Developer Tools

Color contrast: Color contrast should at least pass WCAG AA (AAA for mobile).

🛠 Contrast ratio

Headings

H1: All pages have an H1 which is not the title of the website.
Headings: Headings should be used properly in the right order (H1 to H6).

📹 Why headings and landmarks are so important -- A11ycasts #18

Landmarks

Role banner: <header> has role="banner".
Role navigation: <nav> has role="navigation".
Role main: <main> has role="main".

📖 Using ARIA landmarks to identify regions of a page

Semantics

Specific HTML5 input types are used: This is especially important for mobile devices that show customized keypads and widgets for different types.

📖 Mobile Input Types

Form

Label: A label is associated with each input form element. In case a label can't be displayed, use aria-label instead.

📖 Using the aria-label attribute - MDN

Accessibility testing

Accessibility standards testing: Use the WAVE tool to test if your page respects the accessibility standards.

🛠 Wave testing

Keyboard navigation: Test your website using only your keyboard in a previsible order. All interactive elements are reachable and usable.
Screen-reader: All pages were tested in a screen-reader (VoiceOver, ChromeVox, NVDA or Lynx).
Focus style: If the focus is disabled, it is replaced by visible state in CSS.

📹 Managing Focus - A11ycasts #22

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SEO

Google Analytics: Google Analytics is installed and correctly configured.
Headings logic: Heading text helps to understand the content in the current page.
sitemap.xml: A sitemap.xml exists and was submitted to Google Search Console (previously Google Webmaster Tools).
robots.txt: The robots.txt is not blocking webpages.

🛠 Test your robots.txt with Google Robots Testing Tool

Structured Data: Pages using structured data are tested and are without errors. Structured data helps crawlers understand the content in the current page.

📖 Introduction to Structured Data - Search - Google Developers

🛠 Test your page with the Structured Data Testing Tool

Sitemap HTML: An HTML sitemap is provided and is accessible via a link in the footer of your website.

📖 Sitemap guidelines - Google Support

🛠 Sitemap generator

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Translation

The Front-End Checklist is also available in other languages. Thanks for all translators and their awesome work!

🇯🇵 Japanese: miya0001/Front-End-Checklist