Developer Tools
Regex tester, diff viewer, JSONPath tester, HTML entities reference and more
All 12 developer tools run entirely in your browser. Test regular expressions with live match highlighting, compare two texts or files with a visual diff, query JSON with JSONPath expressions, and look up any HTML character entity — all with zero installation and no server calls.
12 tools
Diff Viewer
Compare two texts line by line and highlight differences
Regex Tester
Test JavaScript regular expressions with real-time match highlighting
JSONPath Tester
Test and evaluate JSONPath expressions against JSON data
HTML Entities Reference
Complete searchable reference for HTML character entities
cURL to Code
Convert cURL commands to code in 10 languages — Python, JavaScript, TypeScript, Go, Rust, Java, PHP, Ruby, Node.js (Axios) and PowerShell
Fake Data Generator
Generate realistic fake data — names, emails, addresses, UUIDs and more. Export to JSON, CSV, SQL or TSV
jq Playground
Test jq filter expressions on JSON data interactively with live output and example filters
JSON Schema
Generate a JSON Schema (draft-07) from any JSON, then validate JSON documents against a schema with detailed error paths
CIDR / Subnet Calculator
Calculate network address, broadcast, host range, subnet mask, wildcard and binary breakdown from any CIDR notation
JSON Diff
Semantically compare two JSON documents — see added, removed and changed fields with full key paths
WebSocket Tester
Connect to any WebSocket server, send messages and inspect frames in real time — with connection status and message log
CSS Specificity Calculator
Parse CSS selectors to display (a,b,c) specificity scores with per-token breakdown and visual bar chart comparison
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About Developer Tools
Essential day-to-day developer utilities. All 12 tools run 100% client-side — no server, no account, no install. Open a tool, paste your data, get your result and move on.
Features
- ✓Regex tester — test regular expressions with live match highlighting, group capture display and flag support (g/i/m/s/u/d)
- ✓Diff viewer — side-by-side and inline text comparison with change highlighting for code, config files and documentation
- ✓JSONPath tester — query JSON documents with JSONPath expressions and see all matching results instantly with a collapsible result tree
- ✓HTML entities reference — searchable, clickable reference for all named HTML character entities (&, <, >, non-breaking spaces and 2,000+ more)
Common Use Cases
- Test and debug a regular expression against sample input with live match highlighting and flag toggling
- Compare two versions of a configuration file or JSON response body with a visual side-by-side diff
- Query a large, deeply-nested JSON response with a JSONPath expression to extract specific values
- Look up the correct HTML entity for a special character (em dash, copyright sign, arrows) without leaving your workspace
Frequently Asked Questions
QIs my data sent to a server?
No. All tools run entirely in your browser. Nothing you paste or type is transmitted.
QWhat regex flavours does the regex tester support?
JavaScript regex syntax (ECMAScript). Flags g, i, m, s, u and d are all supported. Named capture groups, lookaheads, lookbehinds and Unicode property escapes are all highlighted correctly.
QWhat is JSONPath?
JSONPath is a query language for JSON, similar to XPath for XML. Use expressions like $.store.book[*].author or $..price to extract matching values from any JSON document.
QWhat does the HTML entities reference include?
All named HTML5 character entities with their Unicode code points, HTML entity names (e.g. &, ©, é) and a one-click copy button. Search by character, entity name or code point.