Add HTML Processing Instruction docs

[tunetheweb]

Description

Chrome 150 supports Processing Instructions in HTML documents.

Prior to this they were treated as comments by all browsers as noted in the current docs

Warning: ProcessingInstruction nodes are only supported in XML documents, not in HTML documents. In these, a process instruction will be considered as a comment and be represented as a Comment object in the tree.

This warning is now no longer accurate.

Chrome also added some extra methods (getAttribute, getAttributeNames...etc) similar to the equivalents on Element so this PR adds those docs (based on the Element versions).

Motivation

Incorrect and missing docs

Additional details

https://chromestatus.com/feature/6534495085920256

Related issues and pull requests

[github-actions]

Preview URLs (10 pages)

• /en-US/docs/Web/API/Document/createProcessingInstruction
• /en-US/docs/Web/API/ProcessingInstruction/ProcessingInstruction
• /en-US/docs/Web/API/ProcessingInstruction/getAttributeNames
• /en-US/docs/Web/API/ProcessingInstruction/getAttribute
• /en-US/docs/Web/API/ProcessingInstruction/hasAttribute
• /en-US/docs/Web/API/ProcessingInstruction/hasAttributes
• /en-US/docs/Web/API/ProcessingInstruction/removeAttribute
• /en-US/docs/Web/API/ProcessingInstruction/setAttribute
• /en-US/docs/Web/API/ProcessingInstruction/toggleAttribute
• /en-US/docs/Web/API/ProcessingInstruction

External URLs (3)

URL: /en-US/docs/Web/API/ProcessingInstruction
Title: ProcessingInstruction

• https://html.spec.whatwg.org/multipage/parsing.html (1 time) (Note! This may be a new URL 👀)
• https://www.w3.org/TR/xml/ (1 time) (Note! This may be a new URL 👀)

---

URL: /en-US/docs/Web/API/ProcessingInstruction/ProcessingInstruction
Title: ProcessingInstruction: ProcessingInstruction() constructor

• https://www.w3.org/TR/xml/ (1 time) (Note! This may be a new URL 👀)

(comment last updated: 2026-08-13 16:29:44)

[chrisdavidmills]

Nice work here, @tunetheweb. I've left quite a few comments, but these are mainly to do with grammar and page structure stuff. Nothing too serious.

[tunetheweb]

Thanks for the detailed review again @chrisdavidmills ! Think I've addressed it all now.

Many (most?) of the comments you noted were issues with the Element equivalents of these pages (e.g. Element.setAttribute, but given the size of those docs, and issues affect other pages in that section as well, I'm not volunteering to make the same changes there - sorry/not sorry 😊

@noamr could you have a look over this before we merge to make sure I'm speaking the truth here?

[noamr]

Technical LGTM

[tunetheweb]

Just two spots from me @chrisdavidmills . Other than those, happy with your edits.

[chrisdavidmills]

@tunetheweb Verrrrry nearly there. Just a couple more small bits for you to ponder.

[chrisdavidmills]

Aaaaand we're done. Thanks again, @tunetheweb.