Validate any hex color with a regex
Check 3-, 4-, 6-, 8-digit hex formats and preview the RGB(A) channels with a swatch. Runs locally.
/^#(?:[0-9A-Fa-f]{3}|[0-9A-Fa-f]{4}|[0-9A-Fa-f]{6}|[0-9A-Fa-f]{8})$/How to validate a hex color
Type or paste a color. Valid ones surface the RGB(A) channels and a swatch.
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Type a color
All four forms — #rgb, #rgba, #rrggbb, #rrggbbaa — validate.
Patterns compile through the JavaScript RegExp constructor, so syntax errors surface immediately and engine quirks like Unicode property escapes (\p{L}) work when the u flag is on.
patternECMAScriptliteralliveinput · literalvalue · regex#ff8800ccloaded · ECMAScriptPCRE · ready - 02
Pick a sample
Try the dropdown for valid and invalid examples.
Each flag character mirrors the ECMAScript literal: g enables iteration, i folds case, m anchors per line, s lets . match newlines, u unlocks proper Unicode, y is sticky, and d emits indices.
flagsoptionsg · i · mliveconfig · optionssample · flags#fffflags applied · liveECMA · live - 03
Inspect the swatch
Valid colors render a square plus R/G/B(/A) channels.
Watch for catastrophic backtracking on nested quantifiers — a common ReDoS source. The tool caps match counts to keep the page responsive on pathological patterns.
matchgroupshighlightReDoS-saferun · outputpreview · matchesR 255 G 136 B 0matches · livegroups · live - 04
Copy or export
Grab the output as JSON, CSV, or plain text — ready for your editor or pipeline.
Copy writes via navigator.clipboard.writeText; downloads use a Blob and object URL, so nothing transits the network and the output is byte-identical to what you see on screen.
copyexportclipboardblobexport · exportedready · savedCopiedready to shipsuccess
Regex patterns that don't melt down
Use named groups
(?<year>\d{4}) reads better than $1 and survives reordering. Supported in ECMAScript 2018+.
Anchor strictly
Use ^/$ with the m flag when matching whole lines. Without anchors, partial matches sneak through.
Avoid catastrophic backtracking
Nested quantifiers like (a+)+ can explode. Run patterns through ReDoS Detector first.
Escape every literal
Backslash any meta character you want literally: \.\$\^\*\+\?\(\)\[\]\{\}\|\\.
Test edge cases
Empty string, single character, unicode, the maximum length you expect — write fixtures for each.
Patterns aren’t parsers
Don’t parse HTML, JSON, or balanced parens with regex. Use a proper parser when the grammar is recursive.
When to validate hex colors
Design systems, theme imports, CSS audits.
Theme imports
Sanity-check colors from a design tool export. Compiles through the JavaScript RegExp constructor — engine quirks (Unicode property escapes, sticky matching, named groups) work when their flags are on. Error messages cite the exact position of any syntax issue.
ReDoS-safeCSS audit
Confirm a stylesheet uses valid hex throughout. Pairs with the ReDoS detector to catch catastrophic backtracking before you deploy. A pattern that handles 1k-character input fine can become a denial-of-service vector on attacker-controlled 1M-character input.
ECMA-compliantUser input
Validate before saving to a settings store. Output exports as JavaScript, Python re, Java util.regex, .NET System.Text.RegularExpressions, PCRE, and POSIX — language quirks are highlighted on conversion so you don't ship a JS-only pattern to a Go service.
spec-gradeBulk lists
Paste a swatch list and find malformed entries. Capture groups (named or numbered) round-trip cleanly into replacement strings, JSON output, or CSV extraction without re-typing. Backreferences ($1, ${name}) preserve semantics across languages.
cross-engineDocumentation
Verify color tokens in docs match spec. Test against edge cases — empty input, single character, max length, multibyte boundaries — to catch off-by-one and zero-length match bugs before they reach production.
test-readyTeach
Show how #rgba parses into channels. All matching runs client-side so secret patterns never leave the browser. Useful when the pattern itself is sensitive (PII regexes, internal data formats, security filters).
production-readyFrequently asked questions
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Tell us what you need. We ship the top requests every two weeks.