Writing a validation pattern from memory is how subtly wrong regexes enter a codebase.
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Regex Generator
Description
Free · API · MCPToolYour platform
Use Regex Generator three ways
The free Regex Generator on this page works in your browser. The same workflow is available via REST API for apps and via MCP for Cursor, Claude, and other agents — one API key, one plan, one quota. This tool is part of the developer-apis module under Developer Tools.
- Free in browserUse Regex Generator here — no account required.
- REST APICall from your server with
X-Api-Key. - MCP for agentsConnect Cursor or Claude to ToolYour MCP with the same key.
- 1. Get an API keySign in and open Dashboard → API Keys (works for REST and MCP).
- 2. Call or connectUse the REST API from your server, or paste the MCP URL into your agent config.
- 3. Same qualityOutput matches the free web tool across all three surfaces.
What is Regex Generator?
Writing a validation pattern from memory is how subtly wrong regexes enter a codebase. This regex generator returns a curated preset for the six shapes that come up most often — email, http URL, IPv4 address, UUID, digits, and kebab-case slug — together with the flags to use and a note describing precisely what the pattern does not guarantee.
It is deliberately not an AI that writes arbitrary expressions from a prose description. Each preset is a fixed, reviewed pattern with a known trade-off: the email pattern checks shape rather than RFC 5322 compliance, the IPv4 pattern checks four dot-separated groups without range-checking each octet, and the UUID pattern accepts versions 1 through 5. That honesty is the point — you know what you are shipping. Test any preset against your own awkward samples in Regex Tester before it becomes a validation rule.
Browser use is free and needs no signup. The same job runs over REST at POST https://api.toolyour.com/api/v1/developer-apis/regex-generator and over MCP at https://api.toolyour.com/mcp — one API key, one shared monthly credit pool, 1 credit per successful call.
What are common questions about Regex Generator?
Does it write a regex from my description?
No. It returns curated presets rather than generated patterns, so the output is reviewed and predictable instead of plausible-looking.
Which presets are available?
Email, http and https URL, IPv4, UUID versions 1 to 5, digits only, and kebab-case slug. Each comes with its recommended flags.
Why does the email pattern look so simple?
Because full RFC 5322 email matching is impractical and brittle. The preset checks shape, and the note says so — real verification means sending a confirmation message.
What are the key features of Regex Generator?
Six reviewed presets
Common validation shapes with the flags they expect, ready to paste.
Stated limitations
Every preset returns a note describing the cases it deliberately does not cover.
Predictable for agents
A fixed catalogue means an agent gets the same reviewed pattern every time rather than a fresh invention.
How do you use Regex Generator?
Pick the shape
Choose the preset that matches what you are validating.
Read the limitation note
Decide whether the documented gap matters for your use case.
Test before shipping
Run the pattern against your own samples in Regex Tester, then adopt it.
Why presets beat generated patterns
A regular expression is code that runs on untrusted input, and a plausible-looking pattern is more dangerous than an obviously wrong one. Generated expressions fail in two specific ways: they are over-permissive, accepting input the author assumed would be rejected, or they backtrack pathologically on adversarial strings.
A fixed catalogue avoids both. Each preset here has known behaviour and a written limitation, so the decision you make is "is this gap acceptable" rather than "does this pattern do what it claims". When the answer is no, you write a bespoke pattern deliberately and test it — which is the right amount of effort for a rule that will reject real users.
Validation is more than a pattern
Shape matching is the first of three layers and the weakest. Shape — does the string look right, which is what these presets answer. Semantics — does the value exist and belong to this user, which needs a lookup or a confirmation flow. Normalisation — is it stored in one canonical form, lowercased and trimmed, so comparisons behave.
For IP addresses specifically, IP Address Tools does the range checking the preset skips, including private and loopback classification. For slugs, pair the preset with a slug converter so you generate canonical values instead of only rejecting bad ones.
Which core developer tools sit in this cluster?
Where do you browse more developer tools tools?
- Developer Tools tools
Browse the full Developer Tools category on ToolYour.
- Marketing Tools tools
Build UTM links, check ads copy limits, QA email subjects, and calculate ROAS/CPC/CTR — free in the browser; R
- Security Tools tools
Check HTTP security headers, TLS, cookies, JWTs, passwords, hashes, and SPF/DKIM/DMARC — free in the browser;
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