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Front-End Checklist

The perfect Front-End Checklist for modern websites and meticulous developers
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README

🗂 Front-End Checklist

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

Other Checklists:

Tip

⭐️ I've just launched a new curated list for indie developers, feel free to check it out! ⭐️

📚 Table of Contents

How to use?

Important

Disclaimer: This checklist is based on Front-End developers' years of experience, with additions from other open-source checklists.

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:

  • Low indicates that the item is recommended but can be omitted in certain situations.
  • Medium indicates that the item is highly recommended but can potentially be omitted in very specific cases. However, omitting these elements can negatively impact performance or SEO.
  • High indicates that the item cannot be omitted under any circumstances. Removing these elements may result in page malfunctions or cause accessibility and SEO issues. Testing should prioritize 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

Note

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

Meta tag

  • Doctype: High The Doctype is HTML5 and is at the top of all your HTML pages.
<!doctype html><!-- HTML5 -->

The next 2 meta tags (Charset and Viewport) need to come first in the head.

  • Charset: High The charset (UTF-8) is declared correctly.
<!-- Set character encoding for the document -->
<meta charset="utf-8">
  • Viewport: High The viewport is declared correctly.
<!-- Viewport for responsive web design -->
<meta name="viewport" content="width=device-width, initial-scale=1, viewport-fit=cover">
  • Title: High A title is used on all pages (SEO: Google calculates the pixel width of the characters used in the title, and it cuts off between 472 and 482 pixels. The average character limit would be around 55-characters).
<!-- Document Title -->
<title>Page Title less than 55 characters</title>
<!-- Meta Description -->
<meta name="description" content="Description of the page less than 150 characters">

  • 📖 Meta Description - HTML - MDN

  • Favicons: Medium 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">
<!-- Recommended modern favicon format (not recommended for legacy browsers) -->
<link rel="icon" type="image/svg+xml" href="https://example.com/favicon.svg">
<!-- Apple Touch Icon (at least 200x200px) -->
<link rel="apple-touch-icon" href="/custom-icon.png">

<!-- To run the web application in full-screen -->
<meta name="apple-mobile-web-app-capable" content="yes">

<!-- Status Bar Style (see Supported Meta Tags below for available values) -->
<!-- Has no effect unless you have the previous meta tag -->
<meta name="apple-mobile-web-app-status-bar-style" content="black">
<!-- 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>
  • Canonical: Medium 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-read.html">

HTML tags

  • Language attribute: High The lang attribute of your website is specified and related to the language of the current page.
<html lang="en"></html>
  • Direction attribute: Medium The direction of lecture is specified on the html tag (It can be used on another HTML tag).
<html dir="rtl">
  <!-- ... -->
</html>

  • 📖 dir - HTML - MDN

  • Alternate language: Low 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">
  • x-default: Low The language tag of your website for international landing pages.
<link rel="alternate" href="https://example.com/" hreflang="x-default" />

  • 📖 x-default - Google

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

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

  • RSS feed: Low If your project is a blog or has articles, an RSS link was provided.

  • CSS Critical: Medium 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 automates this.

  • CSS order: High 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

Visualize and generate automatically our social meta tags with Meta Tags

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

Note

Using og:image:width and og:image:height will specify the image dimensions to the crawler so that it can render the image immediately without having to asynchronously download and process it.

<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">
<!-- Next tags are optional but recommended -->
<meta property="og:image:width" content="1200">
<meta property="og:image:height" content="630">
<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">

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HTML

Best practices

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

  • 📖 HTML Reference

  • Error pages: High Error 404 page and 5xx exist. Remember that the 5xx error pages need to have their CSS integrated (no external call on the current server).

  • Noopener: Medium 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: Low Unnecessary code needs to be removed before sending the page to production.

HTML testing

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

  • 🛠 W3C validator

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

  • 🛠 Dirty markup

  • 🛠 webhint

  • Link checker: High There are no broken links in my page, verify that you don't have any 404 error.

  • 🛠 W3C Link Checker

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

  • 📖 Use AdBlocking in your Dev Environment

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Webfonts

Note

Using web fonts may cause Flash Of Unstyled Text/Flash Of Invisible Text - consider having fallback fonts and/or utilizing web font loaders to control behavior.

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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. There is also a short Code Guide for consistency.

  • Responsive Web Design: High The website is using responsive web design.

  • CSS Print: Medium A print stylesheet is provided and is correct on each page.

  • Preprocessors: Low Your project is using a CSS preprocessor (e.g Sass, Less, Stylus).

  • Unique ID: High If IDs are used, they are unique to a page.

  • Reset CSS: High 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: Low 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"></div>
</div>

  • embedded or inline CSS: High Avoid at all cost embedding CSS in <style> tags or using inline CSS: only use for valid reasons (e.g. background-image for slider, critical CSS).

  • Vendor prefixes: High CSS vendor prefixes are used and are generated accordingly with your browser support compatibility.

  • 🛠 Autoprefixer CSS online

Performance

CSS testing

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

  • 🛠 stylelint, a CSS linter

  • 📖 Sass guidelines

  • Responsive web design: High All pages were tested at the following breakpoints: 320px, 768px, 1024px (can be more / different according to your analytics). Responsive Checker -

  • CSS Validator: Medium The CSS was tested and pertinent errors were corrected.

  • 🛠 CSS Validator

  • Desktop Browsers: High All pages were tested on all current desktop browsers (Safari, Firefox, Chrome, Internet Explorer, EDGE...).

  • Mobile Browsers: High All pages were tested on all current mobile browsers (Native browser, Chrome, Safari...).

  • OS: High All pages were tested on all current OS (Windows, Android, iOS, Mac...).

  • Design fidelity: Low Depending on the project and the quality of the creatives, you may be asked to be close to the design. You can use some tools to compare creatives with your code implementation and ensure consistency.

Pixel Perfect - Chrome Extension

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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: High 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.

  • 🛠 Use KeyCDN Image Processing for image optimization in real time.

  • 🛠 TinyPNG optimises png, apng (animated png) and jpg images with very small loss in quality. Free and paid version available.

  • 🛠 ZorroSVG jpg-like compression for transparent images using svg masking.

  • 🛠 SVGO a Nodejs-based tool for optimizing SVG vector graphics files.

  • 🛠 SVGOMG a web-based GUI version of SVGO for optimising your svgs online.

  • Picture/Srcset: Medium You use picture/srcset to provide the most appropriate image for the current viewport of the user.

  • 📖 How to Build Responsive Images with srcset

  • Retina: Low You provide layout images 2x or 3x, support retina display.

  • Sprite: Medium Small images are in a sprite file (in the case of icons, they can be in an SVG sprite image).

  • Width and Height: High Set width and height attributes on <img> if the final rendered image size is known (can be omitted for CSS sizing).

  • Alternative text: High All <img> have an alternative text which describes the image visually.

  • 📖 Alt-texts: The Ultimate Guide

  • Lazy loading: Medium Images are lazyloaded (A noscript fallback is always provided).

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JavaScript

Best practices

  • JavaScript Inline: High You don't have any JavaScript code inline (mixed with your HTML code).

  • Concatenation: High JavaScript files are concatenated.

  • Minification: High JavaScript files are minified (you can add the .min suffix).

  • 📖 Minify Resources (HTML, CSS, and JavaScript)

  • JavaScript security: High

  • 📖 Guidelines for Developing Secure Applications Utilizing JavaScript

  • noscript tag: Medium Use <noscript> tag in the HTML body if a script type on the page is unsupported or if scripting is currently turned off in the browser. This will be helpful in client-side rendering heavy apps such as React.js, see examples.

<noscript> You need to enable JavaScript to run this app. </noscript>

JavaScript testing

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Security

Scan and check your web site

Best practices

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Performance

Best practices

  • Goals to achieve: Medium Your pages should reach these goals:

    • First Meaningful Paint under 1 second
    • Time To Interactive under 5 seconds for the "average" configuration (a $200 Android on a slow 3G network with 400ms RTT and 400kbps transfer speed) and under 2 seconds for repeat visits
    • Critical file size under 170Kb gzipped

  • 🛠 Website Page Analysis

  • 🛠 WebPageTest

  • 📖 Size Limit: Make the Web lighter

  • Minified HTML: Medium Your HTML is minified.

  • Lazy loading: Medium 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: Medium 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

  • Third party components: Medium Third party iframes or components relying on external JS (like sharing buttons) are replaced by static components when possible, thus limiting calls to external APIs and keeping your user's activity private.

  • 🛠 Simple sharing buttons generator

Preparing upcoming requests

<link rel="dns-prefetch" href="https://example.com" />
  • Preconnection: Low DNS lookup, TCP handshake and TLS negotiation with services that will be needed soon is done in advance during idle time using preconnect.
<link rel="preconnect" href="https://example.com" />
  • Prefetching: Low 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: Low 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" />

Performance testing

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Accessibility

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

Best practices

Headings

Semantics

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

  • 📖 Mobile Input Types

Form

Accessibility testing

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

  • 🛠 Wave testing

  • Keyboard navigation: High Test your website using only your keyboard in a previsible order. All interactive elements are reachable and usable.

  • Screen-reader: Medium All pages were tested in a screen-reader (VoiceOver, ChromeVox, NVDA or Lynx).

  • Focus style: High If the focus is disabled, it is replaced by visible state in CSS.

  • 📹 Managing Focus - A11ycasts #22

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SEO

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Translations

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

Support

If you have any question or suggestion, don't hesitate to reach me on X:

Contributors

This project exists thanks to all the people who contribute. (Contribute). Contributors

Backers

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Backers

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Sponsors

License

CC0

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