Regex Performance Tester
Compare two regex patterns against your sample text with ops/sec, average match time, match counts and catastrophic backtracking warnings. Free and client-side.
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What is Regex Performance Tester?
Regex Performance Tester is an in-browser benchmark for regular expressions. Paste two patterns, your flags and the text you expect in production, and it times every run to report ops/sec, average match time, match counts and static warnings for backtracking hazards such as nested quantifiers.
Key Benefits
- Catch slow or catastrophic patterns before they hit production traffic
- Objective comparison between equivalent patterns on your own data
- No data leaves the browser, so it is safe for private logs and payloads
Common Use Cases
- •Choosing between two equivalent validation regexes
- •Auditing log-parsing patterns that will run over gigabytes of text
- •Teaching why nested quantifiers cause catastrophic backtracking
How to benchmark a regex
- Paste the patterns: Enter the two regular expressions you want to compare, the flags you use in code, and the sample text they will run against.
- Run the benchmark: Choose an iteration count and press Run benchmark — the tool warms up each regex, then times every run against your sample.
- Read warnings and pick a winner: Compare ops/sec and average time, check the complexity warnings for backtracking risks, and verify both patterns return the same matches.
Key Features
- Side-by-side benchmark of two patterns with warmup and configurable iterations
- Ops/sec and average time per run, auto-formatted in microseconds or milliseconds
- Static complexity warnings for nested quantifiers, greedy dot-star and quantified backreferences
- Match counts and sample matches so you can verify behavior, not just speed
- Fully client-side — sample text never leaves your browser