Language cheatsheet

HTML 5 Cheatsheet

HTML5 page structure, text, links, images, forms, tables and metadata, with accessible patterns.

Page structure

Basic page — A complete HTML5 document with a language, character set and responsive viewport.
Link a stylesheet — Load a CSS file from the head.
Load a script without blocking — defer downloads the script in parallel and runs it after the HTML is parsed.
Use semantic landmarks — Structure the page with elements that screen readers and search engines understand.
Write a comment — Leave a note that browsers do not display.

Add a meta description — Write the summary search engines often show under your title. About 150 characters works well.
Set the canonical URL — Tell search engines which URL is the preferred version of this page.
Add Open Graph tags — Control how the page looks when shared on social networks and chat apps.
Keep a page out of search results — Ask search engines not to index the page.
Add a favicon — Set the icon shown in browser tabs.
Add structured data — Describe the page to search engines with JSON-LD.

Write headings — Use one h1 per page, then h2 to h6 in order without skipping levels.
Create a link — Link to a page. target="_blank" with rel="noopener" opens a new tab safely.
Link to a section of the page — Give an element an id and link to it with a hash.
Add an image — Always include alt text, and width and height to avoid layout shift. loading="lazy" defers off-screen images.
Serve images for different screens — Let the browser choose the best size.
Offer modern image formats — Use WebP or AVIF where supported, with a fallback.
Make lists — Unordered, ordered and description lists.
Embed a video — Play a video file with controls and a fallback message.
Embed another page — Embed content lazily, and restrict what it can do with sandbox.
Add a collapsible section — Show and hide content with no JavaScript.
Create a modal dialog — Use the built-in dialog element. Call showModal() to open it and close() to close it.

Build a form — Label every control. The for attribute matches the input's id.
Choose an input type — The right type gives mobile users the right keyboard and built-in validation.
Validate in the browser — Constrain input with built-in attributes. Always validate on the server too.
Add a dropdown — Offer a list of choices in a dropdown.
Add radio buttons and checkboxes — Radio buttons that share a name allow one choice.
Add a multi-line field — Let users write longer text.
Group related fields — Group controls with a caption, which screen readers announce.
Accept a file upload — A form that uploads files needs the multipart encoding.

Create a table — Use a caption, header cells with scope, and grouped sections.
Add a skip link — Let keyboard users jump past the navigation to the main content.
Name an icon button — Give a button with no text an accessible name.
Store custom data on an element — Attach data that JavaScript can read through dataset.
Write special characters — Escape characters that HTML treats as markup.

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