Regex Tester
Test regular expressions against sample text with live match highlighting and flag support — g, i, m and more.
Data handling: Processing: this tool runs in your browser and does not send entered data to a tool-service endpoint. Site analytics, advertising, or embedded resources may still make separate requests. See the Privacy Policy for site-level details.
About Regex Tester
Regex Tester provides a dedicated, focused workspace: Test regular expressions against sample text with live match highlighting and flag support — g, i, m and more. Using it is a three-step job: 1) Open Regex Tester and review the inputs, units, and data-handling notice shown on its page, 2) Enter the information requested by this tool and adjust only the options that apply to your task, 3) Review the result and use the available copy, download, or reset controls. Built as a focused utility in our developer tools library, it is available in a modern desktop or mobile browser without requiring account registration or software installation.
Regex Tester is a free, browser-based regex tester from ProfitTool. Test regular expressions against sample text with live match highlighting and flag support — g, i, m and more. Review any usage notes shown on this page before relying on its availability. Review the tool's data-handling notice before entering sensitive information; some features store settings locally or contact external services.
People who use Base64 & Base64URL Encoder / Decoder usually reach for this next: Markdown Preview covers the other half of the workflow.
Popular Use Cases
- Case 1Format, validate and diff JSON, XML, YAML and SQL payloads.
- Case 2Debug JWTs, base64 blobs, timestamps and regex patterns quickly.
- Case 3Generate secure UUIDs, tokens, hashes and passwords for staging setups.
- Case 4Prep sample data and mock responses before your backend is ready.
Common Mistakes to Avoid
Pasting production secrets into remote tools
Anything that leaves your machine should be assumed logged. Prefer tools that run locally — verify with the Network tab.
Trusting a decoded JWT payload
Decoding is not verifying. Always validate the signature server-side before acting on claims.
Treating base64 as security
It obscures nothing. Encrypt if the data is sensitive.
If you came here from the Markdown Preview, keep Find and Replace open in a second tab.
Key Terms Explained
- Base64
- An encoding that represents binary data in ASCII. It is not encryption — anyone can decode it.
- JWT
- JSON Web Token: three base64url segments (header, payload, signature) separated by dots.
- Epoch time
- Seconds elapsed since 1 January 1970 UTC — the format most APIs use for timestamps.
- UUID v4
- A 122-bit random identifier with a collision probability low enough to ignore in practice.
Data Handling
Data handling depends on this tool's implementation. Read the Data handling notice above the tool before entering sensitive information. Some features run locally; others contact named providers or ProfitTool services. Site analytics, advertising, and embedded resources may also make separate requests.
Pro Tips & Best Practices
- Check the individual tool's data-handling notice before entering staging secrets or personal data.
- Use ⌘/Ctrl-A to select-all inside the editor before copying results.
- Pair it with your terminal — copy the output straight into a curl or fetch call.
How to use Regex Tester
- 1Open Regex Tester and review the inputs, units, and data-handling notice shown on its page.
- 2Enter the information requested by this tool and adjust only the options that apply to your task.
- 3Review the result and use the available copy, download, or reset controls. Processing and storage behavior vary by tool.
Pairs naturally with the Find and Replace — Base64 & Base64URL Encoder / Decoder is the usual next step.
Frequently Asked Questions
Is it safe to paste secrets or production payloads into Regex Tester?›
Do not paste live credentials into a website unless you have verified the tool's implementation and data-handling notice. Rotate any credential you have already exposed.
Is Regex Tester free to use?›
Yes — Regex Tester is completely free with no signup, watermark, trial or hidden paywall, however often you use it.
Which standards does Regex Tester follow?›
It relies on native Web APIs — TextEncoder, SubtleCrypto, JSON and the URL parser — so output matches what your runtime will produce in Node, Deno or the browser.
Does Regex Tester work on mobile phones and tablets?›
Yes. The layout is mobile-first and tested on iOS Safari, Android Chrome and every current desktop browser, with tap targets sized for thumbs.
What happens if my input is malformed?›
You get a specific parse error with the offending position instead of a silent failure, which is usually enough to spot the missing comma or bracket.
Is my data safe when I use this regex tester?›
Data handling varies by tool. Read the notice above the workspace to see whether your input stays in the browser or is sent to a named provider or service. Avoid entering sensitive information unless you understand that tool's handling.
Can I automate this regex tester in CI?›
This page is interactive, but everything it does maps to a one-line script using the same Web APIs, so porting the logic into a CI step is straightforward.
How is Regex Tester different from other online regex tester tools?›
It does one job without pop-ups, forced sign-in or interstitials, and remembers your settings between visits so repeat work takes seconds.
Why Use Regex Tester on ProfitTool?
Regex Tester sits inside ProfitTool's Developer Tools collection — 250+ tools for engineers, DevOps and API integrators. Review this tool's inputs and data-handling notice before use.
Regex Tester is part of ProfitTool's developer tools collection for engineers, DevOps and API integrators. Review its documented inputs, assumptions, and data handling to decide whether it fits your task.
Guides that explain Regex Tester
Background reading from the ProfitTool Knowledge Hub.