Color Utility
Convert HEX, RGB, HSL colors and check WCAG contrast ratio for accessibility.
Color Conversion
Contrast Checker (WCAG)
The quick brown fox jumps over the lazy dog.
Color Converter and Contrast Checker
Design and frontend work often moves between HEX, RGB, and HSL color formats. This tool converts color values and helps check contrast between foreground and background colors so UI text and controls remain readable.
Common use cases
- Convert CSS colors: Move between HEX, RGB, and HSL when implementing designs.
- Check readability: Compare text and background colors before shipping UI changes.
- Create color variations: Use HSL to adjust lightness or saturation for hover states, borders, and subtle backgrounds.
Accessibility note
Color contrast affects readability, especially on mobile screens and bright displays. Do not rely on color alone to communicate state; combine color with text, icons, labels, or layout cues.
Articles for this tool
Recent Articles
curl Options Cheat Sheet: What -X, -H and -d Actually Do
A reference for the curl options you meet in real API work: why -d already implies POST, how -d differs from --data-raw, the @ prefix that silently reads a file, single vs double quotes, and why -k and -L deserve more caution than they usually get.
Converting Between JSON Schema and Zod: How required Maps to .optional()
Inside a two-way converter that turns JSON Schema into a Zod schema and Zod code back into JSON Schema. Covers the inverted defaults between required and .optional(), the constraint mapping table, and how the Zod side is parsed without executing any code.
SQL Clause Order Reference: Why WHERE Can't See Your SELECT Alias
The order you write SQL clauses is not the order the database runs them. A reference for the logical execution order (FROM → WHERE → GROUP BY → HAVING → SELECT → ORDER BY → LIMIT), why aliases fail in WHERE, when to use WHERE vs HAVING, and the MySQL/PostgreSQL differences that bite.
Unified Diff Format Reference: Reading @@ Hunks in git diff Output
How to read the unified diff format git produces: what the four numbers in @@ -12,7 +12,9 @@ mean, why a one-character edit shows as a whole-line replacement, the whitespace and line-ending traps, \ No newline at end of file, combined @@@ diffs on merges, and rename detection via similarity index.
UTC to JST Reference: The 9-Hour Offset, Cheat Sheet & Timezone Pitfalls
Convert between UTC and JST (Japan Standard Time) with a cheat sheet. Covers what Z and +09:00 mean in ISO 8601, when JavaScript date parsing silently shifts by 9 hours, MySQL/PostgreSQL timezone behavior, and why GitHub Actions cron always runs in UTC.
CREATE TABLE Reference: MySQL vs PostgreSQL vs SQLite Types & Constraints
A cross-database CREATE TABLE (DDL) reference with cheat sheets for data types, auto-increment keys (AUTO_INCREMENT / IDENTITY / rowid), foreign key ON DELETE behavior, and the CHECK constraint that MySQL silently ignores.