Regex Tester Online — Free & Private
Test a regular expression against text with live match highlighting. Free, private, and processed entirely in your browser — no upload, no account, no file ever leaves your device.
How to use Regex Tester
Test a regular expression against text with live match highlighting. Everything runs in this tab — nothing is uploaded for the core job.
- Enter your content — Type or paste what you want to work with — Regex Tester runs immediately in your browser.
- Choose your options — Set any options Regex Tester offers.
- Get your result — Copy or download the result \u{2014} done entirely on your device, nothing uploaded.
Privacy proof for Regex Tester
This tool processes files in your browser. Open DevTools → Network while you run it: your document is not uploaded. After one online visit, many tools keep working with Airplane Mode on (libraries cached locally).
Popular tools
The highest-demand tools with full options — browse by category below for the rest.
Star any tool — it appears under Favorites on this device.
How this actually works
Each tool runs entirely with JavaScript already loaded in this page — PDF tools via pdf-lib and pdf.js, image tools via the browser's native Canvas API, and everything else with plain JavaScript. Your files or input are read into browser memory, processed, and handed back as a download or copyable result. This page itself is served by a small Laravel route; Laravel never sees your files either. The only backend in use is Supabase, and only for two optional things: signing in with a magic link, and — only if you're signed in — a log of which tool you ran and when. Honest limits worth knowing: Compress PDF flattens each page to a re-encoded image (great for scans, not ideal if you need selectable text after); HEIC conversion uses a small on-demand converter when the browser cannot decode HEIC natively (Safari often works without it); Fill PDF Form is best-effort for simple AcroForm fields, not a full Adobe Forms replacement; and Word/Excel/PowerPoint ⇄ PDF genuinely needs a server-side engine, so it isn't included — this build only ships tools that can honestly run client-side.
Questions people actually ask
Which regex flavor does this use?
Your browser's native JavaScript regex engine (ECMAScript) — the same one that runs in real JS code, not PCRE or POSIX, so a pattern that works here is guaranteed to work in JavaScript, though it may differ slightly from a PCRE-flavor tester elsewhere.
What do the g/i/m flags mean?
"g" (global) finds every match instead of stopping at the first; "i" makes matching case-insensitive; "m" (multiline) makes ^ and $ match the start/end of each line instead of only the whole string.
Does it show capture groups?
Yes — when a pattern includes groups (parentheses), each match's groups are listed in the copyable summary alongside the full match.
What happens if my pattern is invalid?
You'll see the browser's own regex parser error message directly, so you know exactly what's wrong instead of a silent non-match.
Does matching update live as I type?
Yes — both the pattern and test string update the highlighted matches instantly, no separate run step needed to see results.
Can I test multiline text?
Yes — the test string is a full textarea, and the "m" flag controls whether ^/$ match per-line or only at the very start/end.
Is there a text length limit?
No fixed limit — very long test strings just take proportionally longer to match against, since it all happens in your browser.
Is my pattern or text sent anywhere?
No — matching happens entirely in your browser using JavaScript's built-in RegExp; nothing is transmitted.
Is this really free, and is there a file size limit?
Yes — no account, no paywall. Since processing happens in your browser's memory rather than uploading anywhere, the practical limit is your device's available RAM, not a server quota. Very large files (500+ pages) may run slower, especially for Compress and PDF→JPG.
Does anything about my file get sent anywhere?
No. Every tool runs with pdf-lib/pdf.js loaded in this page; your file is read into browser memory and never leaves it. The only network call this app makes for your account is Supabase auth — and that only stores which tool you ran and when, never file content.
Why isn't Word/Excel/PowerPoint → PDF included?
Converting Office formats accurately needs a real rendering engine (what Word or LibreOffice use internally) — no browser library does this reliably. Rather than ship a broken version, it's left out.
Does TechDriven Tools have OCR (text recognition)?
Yes — OCR PDF recognizes text in scanned or photographed pages using Tesseract.js, running entirely on your device, and gives you a searchable PDF or a plain text file. Nothing is uploaded for this either.
Can I use this without an internet connection?
Once the page and its libraries have loaded once, yes — the tools themselves need no network access. Signing in and viewing history do require a connection, since those talk to Supabase.
What happens to the "history" if I sign in?
Only a row per tool run — the tool's name and a timestamp. No filename, no file content, ever. You can see the full list any time via the History button.
Are the non-PDF utilities (password generator, JSON formatter, etc.) private too?
Yes — same rule as the PDF tools. Word Counter, Case Converter, Password Generator, UUID Generator, Base64, Hash Generator, JSON Formatter and JWT Decoder all run with plain JavaScript already loaded in this page; nothing you type or paste is sent anywhere.
Regex Tester, in depth
Test a regular expression against text with live match highlighting, right as you type.
Features
Live Matching
See matches highlighted as you edit the pattern or text.
Standard JS Regex
Uses the browser's own regex engine — what you test is what your code will actually run.
Match Count
See exactly how many matches a pattern produces.
Instant
No network call — matching happens locally.
Why use Regex Tester
- Debug a regex that isn't matching as expected before it goes into production code.
- Build a pattern incrementally, seeing results after every keystroke.
- Validate an input format — emails, phone numbers, custom IDs — against real sample data.
- Learn regex syntax by experimenting safely against your own text.
How it works
This runs your pattern through the browser's own native regular expression engine — the exact same engine JavaScript code in a real application would use — so a pattern that works here behaves identically once it's in your codebase, with no separate regex dialect to account for.
A note on regex flavors
Regex syntax varies slightly between languages (JavaScript, Python, PHP, and others each have small differences). Since this tool uses JavaScript's own engine, it's an exact match for testing patterns meant for JavaScript code, and close enough for most other languages' patterns — just double-check anything using flavor-specific features before assuming perfect portability.
Why people search for Regex Tester
Test a regular expression against text with live match highlighting. Searchers looking for “Regex Tester free” or “Regex Tester no upload” usually want speed plus privacy — that is exactly the TechDriven Tools model.
Regex Tester sits in our Developer Tools group. The page is built so you can finish the job without creating an account, installing a desktop pack, or sending the payload to an unknown converter API.
Who Regex Tester is for
- You need a result now and do not want another account wall.
- The file or text is sensitive enough that uploading feels wrong.
- A desktop suite is overkill for a one-page or one-photo job.
- You want a second opinion after another converter produced a weird output.
Recommended workflow
Paste only what you intend to transform → run locally → copy into your editor or terminal → never paste production secrets into random upload sites.
- Open Regex Tester (also available from category hubs and ⌘K).
- Use the labeled fields or dropzone — options match what Regex Tester actually does.
- Run the tool and wait for local progress to finish.
- Download or copy the result, then verify on the device where you will share it.
Tips that improve results
- Rename the output with date + purpose before you attach it to email.
- On phones, plug in power for large PDFs, videos, or spreadsheets.
- Prefer UTF-8 text for developer converters; weird encodings cause most “broken” results.
- Start with a non-sensitive sample so you learn the options before the real file.
- Change one setting at a time when you are comparing quality or layout.
- Keep the original until stakeholders accept the download.
Common mistakes with Regex Tester
- Expecting Regex Tester to replace a full desktop suite for every edge-case format.
- Skipping a sample check and discovering a bad export after the original was deleted.
- Chaining many lossy image/PDF steps when one careful pass would have been enough.
- Using a public computer without clearing downloads afterward.
Privacy model
Processing for Regex Tester is designed to stay in the browser. Laravel serves the page; it does not receive your file bytes for conversion. Optional Supabase auth only stores which tool you ran and when — never filenames or contents.
Related tools
- Password Generator
- Base64 Encoder/Decoder
- Hash Generator
- JSON Formatter
- JWT Decoder
- QR Code Generator
FAQ — Regex Tester
Is Regex Tester free to use?
Yes. Regex Tester on TechDriven Tools is free — no account, no watermark, and no paywall for the core workflow.
Does Regex Tester upload my file or text?
No for processing. Regex Tester runs in your browser tab. Optional sign-in never stores file contents — only tool names and timestamps if you enable history.
When should I use Regex Tester?
Use Regex Tester for Developer Tools jobs where privacy and speed matter: quick one-offs, sensitive inputs, or checking another app’s result without another upload site.
Will Regex Tester work on my phone?
Yes in a modern mobile browser. Large inputs can take longer because your device does the work locally.
What are the limits of Regex Tester?
There is no server quota from us. Limits are your device memory, battery, and formats the browser can decode. Regex Tester will not pretend to support server-only Office or cloud-AI pipelines.
How is Regex Tester different from upload-based sites?
Upload converters send your content to someone else’s server. Regex Tester keeps the transform on-device whenever the format allows, which is the safer default for confidential documents, photos, tokens, and configs.
Bottom line
If you need Regex Tester done quickly and privately, start at /regex-tester, run it once on a sample, then process the real input. That is how TechDriven Tools stays competitive: honest capabilities, labeled UI, and content that matches what the tool actually ships.
From our blog: How to Test Regular Expressions Online