Web & developer
Regex, tokens, cron lines and API payloads, checked locally. Nothing leaves the tab.
10 tools · free · no upload
- Regex matches the wrong textRegex tester
- Token expired, or is it valid?JWT decoder
- Cron runs at the wrong timeCron explainer
- Does my JSON fit this schema?JSON Schema validator
- What changed in this JSON?Compare JSON
- What does this SQL do?SQL query visualizer
- Is this page accessible?Accessibility checker
- Which CSS rule wins?Specificity calculator
- Webhook signature check failsWebhook signature tester
- Build a call to this APIOpenAPI request builder
How the developer tools work
Paste a pattern, a token or a payload and it is checked as you type, in this tab. Signatures are computed with the browser’s Web Crypto, and HTML is read without running its scripts. No request leaves the page, so a production token or a webhook secret is never sent anywhere.
Which tool for which problem
- A pattern does not match what you expect: test the regex with highlighted matches and a plain-English explanation.
- You got a token from an API: decode the JWT, check when it expires and verify its signature.
- A job runs at odd times: explain the cron expression and list its next runs.
- A payload is rejected: validate it against its JSON Schema, or compare it with one that works.
- A webhook signature fails: find out why for GitHub, Stripe, Slack, Shopify or any HMAC.
- An API has an OpenAPI file but no examples: build the request as curl, fetch or Python.
- Someone else’s SQL is hard to follow: visualize the query step by step.
- A page may be hard to use with a screen reader: check its accessibility.
- A CSS rule is ignored: calculate the specificity and see which rule wins.
Questions
Is my token, key or payload sent anywhere?
No. Everything is computed in this browser tab and the page makes no network request with what you paste. You can load the page, go offline and use it.
Can these tools call my API?
No. They build and check requests, signatures and payloads; you copy the result into your terminal or your code and run it yourself.
Which flavours do the tools follow?
The regex tester uses JavaScript’s own engine, the JSON Schema validator follows drafts 2020-12, 2019-09 and 07, and the SQL visualizer reads standard SQL plus common MySQL, PostgreSQL and SQL Server spellings.