Developer Tools
Extract CSS Containment Values
Extract CSS containment, container, content-visibility, and contain-intrinsic-size declarations from pasted stylesheets without rendering, fetching, or uploading code.
0 / 30,000 characters. No upload, storage, or account required.
CSS containment extraction workflows
Use this extractor when pasted styles need a browser-local inventory of containment and rendering-performance declarations before QA, migration, or documentation.
Audit container-ready components
Pair containment rows with Extract CSS Container Queries, Extract CSS Supports Rules, and Extract CSS Layer Names.
Review rendering performance
Use Extract CSS Property Names, Extract CSS Media Queries, and CSS Formatter while checking performance-related CSS.
Clean copied output
Send extracted rows to Remove Duplicate Lines, Sort Lines, or Normalize Whitespace.
What this tool does
Extract CSS Containment Values scans pasted CSS as text, lists containment and rendering-performance declarations with source lines, removes duplicate rows, and runs locally in your browser.
Common use cases
Extract CSS contain, container, content-visibility, contain-intrinsic-size, and will-change declarations from pasted stylesheets, component CSS, performance experiments, framework output, or copied source before rendering-performance audits, container-query cleanup, migration, or documentation handoffs.
Use Extract CSS Containment Values when you are working with copied API payloads, logs, encoded values, config snippets, identifiers, or debugging data and need a quick browser-local check before pasting the result into docs, tickets, tests, or another developer tool.
How to use it
- Paste CSS, component styles, container-query experiments, performance work notes, or copied source that contains containment declarations.
- Choose whether duplicate rows should be removed and whether values should be normalized for comparison.
- Review extracted rows with source lines, then copy the clean list for rendering-performance audits, container-query cleanup, migration, or documentation handoffs.
Example workflow
Copy a small payload or encoded value from an API response, request URL, log line, or config file. Run the focused check here, confirm the output is readable, then continue with related developer data tools such as validation, formatting, decoding, timestamp conversion, or CSV/JSON conversion.
Privacy note
Extract CSS Containment Values runs locally in your browser. Your pasted CSS is not uploaded, rendered, fetched, crawled, executed, stored, or logged.
FAQ
Does Extract CSS Containment Values measure performance?
No. It scans pasted CSS as text and does not render pages, benchmark layout, execute code, fetch assets, upload, store, or log snippets.
Which containment declarations are included?
It finds contain, container, container-name, container-type, content-visibility, contain-intrinsic-size variants, and will-change declarations.
When is this useful?
Use it while auditing rendering-performance CSS, container-query migrations, component isolation, or documentation for layout containment patterns.
Explore more tools
Browse the Developer Tools hub or continue with the Developer Data Toolkit when this task is part of a larger workflow.