CSS Variable Extractor — Find & Audit Custom Properties
Extract CSS custom properties (--variables) from a stylesheet and find unused or undefined references.
How it works
- 1Paste or type your text in the input field
- 2Click "Process" — processing happens in your browser
- 3Copy the result or download as a text file
What to do next
About CSS Variable Extractor
CSS Variable Extractor is a free, in-browser developer tool. Extract CSS custom properties (--variables) from a stylesheet and find unused or undefined references. The page exposes a small surface — input, controls, output — so a first-time visitor can complete the job without reading documentation.
The right moment to reach for CSS Variable Extractor is when you have a focused developer utility job that fits inside a browser tab. Open the page, drop in the file or paste your input, choose the options that matter, and the tool returns the result.
The execution path is auditable from the page itself: open developer tools, switch to the Network tab, run a job. The requests you see are static-asset GETs for the engine and the page resources. The actual work is JavaScript code running against the bytes already in your tab's memory.
Behind the controls you see, standard browser APIs is doing the actual developer utility. Formats are detected on load and the engine produces a deterministic output for any given input + options combination — useful when you need to re-run a job and expect identical results.
On limits: 0 MB per file is the ceiling. Output formats and quality settings are listed in the controls panel above, and they apply to every run.
The heaviest users of CSS Variable Extractor tend to be students learning new languages, QA engineers writing repro cases and devops engineers crafting one-liners. Each group brings slightly different expectations to the tool, but the same single-page architecture serves every one of them with the same response time.
The download is delivered as a clearly named file the moment processing completes — no email link, no "your result will be ready in 5 minutes" queue, no expiry timer. The file is generated in your browser and saved by your browser's normal download flow.
As a workflow component, CSS Variable Extractor is the part you reach for when a single, well-defined developer utility step needs to happen. It performs that step and returns a standard file you can carry into the next part of your pipeline.
CSS Variable Extractor is built around steady iteration on a small set of options rather than feature creep. Every additional setting attracts a slightly different audience, but a long settings panel makes the common case slower for everyone. The current controls reflect what users of the tool actually use.
Some context on why CSS Variable Extractor exists in this form: modern File APIs, high-performance JavaScript engines, and well-maintained open-source libraries now make it possible to perform developer utility work entirely in the browser. CSS Variable Extractor is built on top of that capability, which is why a single page can host the full pipeline.
If you also use a command-line tool for css variable extractor, CSS Variable Extractor is a convenient alternative for the times you are on a different machine or helping someone who is not comfortable in a terminal. The output is a standard file in the format documented above.
Pro tip: CSS Variable Extractor works just as well in a private/incognito window as in a normal one, which is occasionally useful when you want zero browser-history footprint of the job. Another tip: if the tool ever feels slow, it is almost always because the browser tab is competing for CPU with another tab — pausing or closing the heavy ones gives the engine room to work.
When something goes wrong, the cause is usually one of three things: a malformed input, a browser that is out of memory, or a corporate proxy that is interfering with the page's static assets. The first two are easy to diagnose; the third typically requires asking your IT team to allow standard browser APIs to load.
Open the workspace above to start using CSS Variable Extractor. The engine loads on the first interaction so the page itself stays light, and once the tool is warm it processes subsequent jobs quickly. The moment the page is interactive, the tool is ready to do real work on your file.
How it works
- 1Open the CSS Variable Extractor workspace above. The interface is a single page, so there is nothing to navigate.
- 2Select the developer file you want to process — drag-and-drop and the file picker both work.
- 3Pick any non-default settings you need. Most users leave the defaults alone for the first run and only revisit if the result needs tuning.
- 4Click to start the job. The engine (standard browser APIs) processes the input in the page; you can watch the progress indicator until it completes.
- 5Save the output when it is ready.
- 6Re-run with different settings as often as you want. Each run produces a fresh output and the original file on disk is never modified.
Common use cases
- Inspect a payload during local development without writing a script using CSS Variable Extractor.
- Generate a quick fixture without leaving the browser.
- Encode binary content for transport in a JSON body.
- Hash a string for a quick reproducibility check.
- Decode a token to confirm its claims during a debugging session.
- Pretty-print a minified blob during incident triage.
- Format a noisy log line into something a teammate can read.
- Convert between data formats while wiring up an integration.
FAQ
What are CSS custom properties?
Variables defined with -- prefix (e.g. --primary: blue) and used via var(--primary) in your CSS.
What does "unused" mean?
A variable that is defined (--name: value) but never referenced with var(--name) in the same stylesheet.
What about variables defined in other files?
Paste all your CSS together, or check "undefined" references which may be defined elsewhere.
Does it handle fallback values?
It detects var() usage; fallback values inside var(--name, fallback) are noted but not separately tracked.
Can I export the variables?
Copy the output directly — it lists all variables in a format you can paste into a :root block.
Is my data safe?
All processing happens in your browser.
What does the error message in CSS Variable Extractor mean?
Failures usually fall into one of three buckets: the input is in an unsupported format, the input is over the size cap, or the input is structurally malformed (a truncated download, a partial export, or a stream the engine does not recognise). The first two are easy to confirm — check that your file is in a supported format and that it is below 0 MB. For the third, opening the file in its native viewer first is the fastest way to confirm the source is intact.
Are jobs run with CSS Variable Extractor stored anywhere?
Favtoo keeps no copy of your file because Favtoo never receives your file. CSS Variable Extractor runs entirely in your browser, the input is held only in your tab's memory, and closing the tab discards it. There is no opt-in cloud history, no "recent jobs" panel synced to an account, and no server-side retention to configure — the architecture simply has nowhere for your file to be stored.
What does CSS Variable Extractor do that command-line tools do not?
Desktop apps usually have more advanced features but require installation, maintenance and (often) a licence. Paid online tools are convenient but route your file through their servers and gate downloads behind accounts. CSS Variable Extractor sits in between: free, instant, and private, but intentionally narrow in scope. For one-off jobs and the common developer utility operations, it is usually the lowest-friction choice; for highly specialised work, a dedicated app is still the right answer.
Does CSS Variable Extractor work in Safari, Firefox, Chrome and Edge?
CSS Variable Extractor works in any modern browser released in the last few years — Chrome, Edge, Firefox, Safari, Brave, Arc and the major Chromium derivatives are all supported. The underlying engine relies on widely-supported web APIs, so there is nothing exotic to install. If you are on a very old browser version and the tool fails to load, updating to the latest release of your preferred browser is the only fix needed.
How do I know I am using the latest version of CSS Variable Extractor?
CSS Variable Extractor is updated whenever the underlying engine releases an improvement or a bug fix. Because the tool is delivered as a static page, every visit fetches the latest version automatically — there is no "version" to manage on your end. If a particular release ever changes default behaviour, the change is documented on Favtoo's changelog so you can confirm what shifted.
Can I use CSS Variable Extractor with formats other than the defaults?
The accepted formats are listed in the upload area on the tool itself. If your input is in a format that is not directly supported, convert it first using one of Favtoo's converter tools — every Favtoo converter outputs a file that is a clean input to the next tool in the chain.
How many times per day can I use CSS Variable Extractor?
Inputs are capped at 0 MB per file, which keeps memory usage stable across phones, tablets and older laptops. You can run CSS Variable Extractor as often as you need; every run produces a full-quality result.
Will I notice a difference in the output from CSS Variable Extractor?
CSS Variable Extractor is built to preserve quality wherever the underlying developer format allows it. Operations that are mathematically lossless (e.g. structural transformations, lossless re-encoding) round-trip with no perceptible change. Operations that involve a lossy codec inevitably introduce small artefacts at the byte level, but the defaults aim at the sweet spot where output looks or sounds the same to a normal viewer or listener while still being meaningfully smaller or faster than the input.
Does CSS Variable Extractor ask for any browser permissions?
CSS Variable Extractor only needs the standard web platform — file picker access for the inputs you choose to load, and optionally clipboard access if you copy the result rather than downloading it. There is no microphone, camera, geolocation or background-permission request, because none of those are needed for the work the tool does.