uxlint

uxlint

Audit any website's UX the way a design-literate reviewer would: contrast, tap targets, type scale, colour discipline, scan patterns, landmarks. Every finding comes with a prescriptive fix an agent (or a human) can apply directly. It's designed to sit in a coding agent's loop (MCP) and be iterated against until green.

[An agent audits a pricing page, gets a contrast error and a colour-clash finding with fixes for each, applies them, re-checks the rule, and re-grades the page from B to A]

A real run, start to finish: audit_url → Grade B, a 2.39:1 contrast error and three CTAs in three different accent hues → the fix → verify_fix → Grade A. Every number in it came back from the tools; only the waiting was cut.

This is the CLI: a small, single static Rust binary. It drives a Chrome/Chromium you already have installed over the DevTools protocol (no Node, no Playwright, no headless-browser download), captures what a page looks and reads like, and sends that to uxlint's hosted server, which does the actual grading. The rules engine, the calibrated thresholds, and the LLM judge all live server-side, so the client never needs updating when a rule changes.

┌──────────────────────────┐        POST /v1/audit {snapshots}        ┌──────────────────────────┐│ uxlint (this binary)     │ ───────────────────────────────────────▶ │ uxlint-server (hosted)    ││ drives YOUR Chrome (CDP) │ ◀─────────────────────────────────────── │ rules engine + LLM judge  │└──────────────────────────┘        report {findings + fixes}         └──────────────────────────┘

Install

curl -fsSL https://uxlint.net/install.sh | sh    # detects OS/arch, verifies checksum

Or with mise — its github backend pulls the matching build from GitHub Releases, verifies it, and updates on mise up:

mise use -g "github:uxlint-net/uxlint-cli[rename_exe=uxlint]@latest"

or pin it in a project's mise.toml:

[tools]"github:uxlint-net/uxlint-cli" = { version = "latest", rename_exe = "uxlint" }

Or build from source (needs a recent stable Rust toolchain and a Chrome/Chromium on PATH):

git clone https://github.com/uxlint-net/uxlint-cli && cd uxlint-clicargo build --release./target/release/uxlint --version

Quickstart

uxlint auth login                                        # opens your browser, saves a tokenuxlint audit --base https://your-site.com --routes /,/pricing

First time auditing your own project? uxlint init picks (or creates) a site to attach reports to and writes a uxlint.toml so every future audit in this directory just works:

uxlint inituxlint audit --base http://localhost:5173 --routes /,/pricing

Exit code 1 on findings above the configured severity → drop it straight into CI (see .github/workflows/ for a template, or the uxlint-net/uxlint-action GitHub Action).

Hiding elements from an audit (uxlint-hide)

Some on-page chrome isn't product UI and shouldn't be judged: a dev/staging environment banner, a "DEV" marker, a debug toolbar, a Storybook/preview affordance. Add the class uxlint-hide to any such element and the audit removes it — it's display:none from first paint, so it never appears in a screenshot and is invisible to the collector (it seeds no findings):

<div class="env-banner uxlint-hide">STAGING</div>

The class is inert on your real site — it does nothing unless the audit is running, because the stylesheet that hides it (.uxlint-hide { display: none !important; }) is injected only by uxlint's browser, before the page's own scripts run. Style your element however you like the rest of the time. It applies in every capture path — the crawl, goal-walk tests, and fix previews.

Does it change anything? (--allow-mutation)

Interaction audits navigate, read, and click candidate menu, disclosure, and dialog controls. Discovery skips controls whose accessible name contains a recognised action verb: delete, remove, accept, leave, revoke, cancel, transfer, pay, publish, submit, add, create, save, and their relatives, matched as whole words anywhere in the label. A label cannot prove what its click handler does, so run interaction audits against an environment you control with disposable data.

Two probes do write, and both need --allow-mutation on top of --states:

• the action-feedback probe clicks a constructive action (Add / Create / Save) to check the page says something happened;
• the destructive probe clicks Delete / Remove and clicks through the confirm dialog, to check the contract that a destructive action either confirms first or offers undo.

They power action-no-feedback, destructive-no-confirm and undo-missing, and those three rules stay quiet without the flag. Throwaway environments only. Being signed in as a user who is allowed to delete a row is not the same as having asked us to, and this flag is where you say so.

uxlint mcp never sets it, and cannot be asked to.

The other way an audit writes is one you wrote yourself: a declared [[tests]] walk signs in as a persona and exercises real flows, which is what a test does.

MCP (use it from a coding agent)

Claude Code, one command:

/plugin marketplace add uxlint-net/uxlint-cli/plugin install uxlint@uxlint

That installs the uxlint MCP server and, if the CLI isn't already on your PATH, fetches the matching version once with the same checksum-verifying installer as above — so /plugin update updates the CLI underneath it too. No Node needed: it downloads one static binary (verified against a published checksum) and drives the Chrome you already have.

Any other agent — one line (the npm package fetches the binary for your platform, verifies the checksum published beside it, and hands over). This is the only route that needs Node 18+, for npx itself; if you'd rather not, install the binary with the line at the top and register that:

claude mcp add uxlint -- npx -y @uxlint-net/uxlint mcp

Or, for a client that reads a JSON config:

{ "mcpServers": { "uxlint": { "command": "npx", "args": ["-y", "@uxlint-net/uxlint", "mcp"] } } }

uxlint is also in the MCP Registry as io.github.uxlint-net/uxlint, for clients that browse it. Already have the CLI? uxlint mcp install registers it directly, no npx wrapper.

There is no token to set up first: ask your agent to audit something while signed out and it hands you a sign-in link that mints and saves the token for you (UXLINT_API_KEY is for CI, which has no browser).

Five tools: audit_url (full audit, graded verdict + action plan), verify_fix (recheck one rule on one page after an edit), get_shot (fetch a finding's annotated screenshot), ux_guidance (best-practice guidance to read before building UI), and lint_feedback — opt-in and off by default (§ Privacy) — one tool for three kinds of signal: whether a finding was useful, a lint uxlint is missing, or a component library it didn't recognise. The agent audits, reads the fixes, edits, and re-audits until green.

Verification and design memory

verify_fix returns passed, failed, not_evaluated or inconclusive. Zero findings alone never means a fix passed. Passing verification currently covers page-title-missing, html-lang-missing and horizontal-overflow, with explicit evidence for the requested route and both viewports. Other checks can report failures but need a full audit and evidence review; unknown rules, skipped checks and old servers cannot pass. A cleared check never submits an automatic acceptance vote.

Keep approved project decisions in uxlint.design.json beside uxlint.toml. ux_guidance reads it afresh each time, including in a new agent session. Start with a draft:

{"version":1,"revision":1,"status":"draft","site":"example.test", "tokens":{"accent":"var(--color-brand)"}, "components":{"primary_action":"Reuse PrimaryButton"}, "pages":{"/":"Explain the product and offer a clear starting action"}, "journeys":["Start the main task from the homepage"], "references":["/styleguide"],"exceptions":[]}

Set site to the project's configured site. Review the decisions with the owner before setting status to approved and committing the file. Increment revision for subsequent approved changes. The tool never approves or writes the contract; drafts do not become guidance. References are not automatically fetched, exceptions do not suppress lints, and this initial local memory does not yet enforce tokens or compare screenshots. Invalid contracts produce a visible warning. Keep the file below 32 KiB and do not put credentials or private customer data in it.

Privacy & trust

This CLI runs on your machine and drives a real browser against real pages, so it's fair to ask exactly what it captures and where it goes. What we can tell you, because it's what the code in this repo actually does:

• The collector is baked in and readable. It's compiled into this binary (include_str! of assets/collector.js), so uxlint --version pins the exact capture code and the server can't inject anything at run time. Everything it captures is page geometry, visible text, computed styles, and screenshots. For an embedded <iframe> it records the src's host only — never the full embed URL, which can carry session ids and tokens in its query string. It never reads your source code or your filesystem beyond uxlint.toml. It does read a little project provenance and send it with the report: your current git commit sha and branch name (git rev-parse), the machine's hostname, and, in GitHub Actions, the repo/PR/commit link. Set UXLINT_RUNNER to override the hostname.

• Secret & PII redaction is best-effort, not a guarantee. Before anything is uploaded, the collector masks text that looks like a token, API key, password, or email address in captured page text, and redacts the same patterns from console logs and native dialog messages. All channels share one pattern list (assets/redact.js), so they can't drift. Screenshots get an extra pass right before capture: every form field value is masked (passwords blanked, other inputs replaced with dots) and pattern-matched secrets in on-page text are scrubbed, so typed data and displayed keys don't land in the image. That pass reaches into shadow DOM (including closed roots, via an attachShadow interceptor) and same-origin iframes, and covers a cross-origin iframe with an opaque box since its pixels can't be redacted. But redaction is pattern-based, and a screenshot is still pixels: arbitrary displayed content that no pattern catches (a customer name on the page, order data), split-up values, and anything drawn into images or <canvas> can still slip through. Credentials you pass with --header/--storage/--login-* drive your browser only and are never sent to uxlint's server.

  Because a report captures page HTML, text, and screenshots, it is impossible to fully guard against sensitive content leaking into it. Use TEST accounts, not real or production ones. For local development the risk is low, as long as the data is only local development data. When you audit an authenticated site that holds real secrets or personal data, review what gets sent before you send it: use --dry-run to write the exact payload (page text, provenance, and screenshots) to a local folder and inspect it without uploading. Redaction reduces accidental exposure; it is not a security boundary, and you remain responsible for what you point uxlint at.

• Navigational text is scrubbed for secrets only, on purpose. Control labels, menu and <select> options, and workspace/org switcher names run through the same secret patterns, but they are not redacted for names or other arbitrary content. The reason is the goal walk: an audit drives the page with an LLM that reads exactly this text to find the right control, operate it, and match its choice back to the DOM. Masking it would defeat the walk, because the judge could no longer tell two options apart or click the one it picked. So the labels an audit needs to navigate stay readable, and a real name that rides along in one of them is covered by the test-accounts rule above rather than by redaction. This is a deliberate trade: keeping the goal walk working is worth more than blanking text the test-accounts rule already protects.

• No telemetry. This binary makes outbound calls to exactly the hosts you tell it to: the uxlint API server (--server/UXLINT_SERVER, or the default hosted origin), the site you ask it to audit, and, only if you explicitly opt in, anonymous rule-feedback signals. There is no separate analytics/crash-reporting/phone-home destination baked in anywhere.

• Feedback is opt-in, off by default. uxlint init asks once; it only ever writes feedback = true to uxlint.toml if you say yes, and you can flip it back at any time.

• The audit browser uses an ephemeral profile. Each audit launches Chrome with a fresh, throwaway user-data directory, so no cookies, history, or extensions from your everyday browsing are ever loaded into the audited session, and nothing persists after the process exits.

• Your login stays local. uxlint auth login stores a token at ~/.config/uxlint/credentials, chmod'd 0600. It's never logged, never printed (except the one deliberate case: uxlint signup prints a freshly minted key so you can export it), and never bundled into a report.

This isn't a substitute for reading the source. It's short, and that's rather the point of publishing it. If you find something that doesn't match this description, please open an issue.

What this CLI is not

It's deliberately dumb: navigate, run the baked-in collector, upload the snapshot, print the report. The rules, thresholds, and judge model are not in this repo and never will be. They're the actual product, and they live server-side only. A build of this CLI is useless without a uxlint server to talk to (the hosted one at https://uxlint.net by default, or your own).

License

Apache License 2.0 (see LICENSE). Read it, audit it, fork it, build it from source, ship it inside your own tooling — no conditions beyond the usual attribution and patent terms.

This used to be the Business Source License, which converted to Apache-2.0 on a Change Date in 2030; we've simply arrived early. The restriction it carried — no competing hosted "audit my site" service built on this code — was protecting the wrong thing: what's valuable is the rules, the calibrated thresholds and the judge, and those are server-side and not in this repo. What IS here is a client that needs a uxlint server to be worth anything, and a client is exactly the piece that should be frictionless to install, read and vendor.

Releases up to and including v0.1.30 were published under BUSL-1.1; v0.1.31 onward are Apache-2.0.