Online Developer Testing & Analysis Tools
Test, debug, and analyze code and data directly in your browser. Regex tester with live highlighting, diff checker, HTTP status reference, password strength, CRON validator, semver checker, readability scorer, and 30+ more.
37
tools
Free
always
100%
browser-based
0
data stored
Regex Tester
Test regular expressions with live match highlighting.
CRON Expression Tester
Validate CRON expressions and preview the next scheduled run times.
Text Diff Viewer
Compare two text blocks side by side and highlight differences.
Word & Character Counter
Count words, characters, lines, sentences, and estimate reading time.
Text Case Converter
Convert text between camelCase, snake_case, PascalCase, kebab-case, and more.
Byte Size Calculator
Calculate the UTF-8 byte size of any string or payload.
HTTP Status Reference
Quick reference for all HTTP status codes with descriptions.
User-Agent Parser
Parse and decode browser and device User-Agent strings.
JSON Path Tester
Test JSONPath expressions against JSON data and inspect results.
IP Subnet Calculator
Calculate network address, broadcast, host range, and CIDR notation.
Chmod Calculator
Convert Unix file permissions between symbolic and numeric modes.
Semver Analyzer
Parse, compare, and validate Semantic Versioning strings.
Line Sorter
Sort, deduplicate, and shuffle lines of text.
Find & Replace
Find and replace text with plain text or regex patterns.
Percentage Calculator
Calculate percentages, discounts, increases, and decreases.
CSV Viewer
Upload and preview CSV files as an interactive table.
JSON Diff
Compare two JSON objects and highlight added, removed, and changed keys.
Password Strength Checker
Analyze password strength, entropy, and estimated crack time.
Readability Score
Analyze text readability with Flesch-Kincaid and other scores.
ASCII Table
Full ASCII and extended character reference table with hex, decimal, and binary.
Color Contrast Checker
Check foreground/background color contrast ratios against WCAG AA and AAA.
Number Formatter
Format numbers with locale, currency, decimals, and thousands separators.
ENV File Parser
Parse .env files — extract key/value pairs, detect syntax errors, and export as JSON.
CSS Specificity Calculator
Calculate the specificity score (IDs, classes, elements) for any CSS selector.
Text Repeater
Repeat any text N times with a custom separator.
Open Graph Preview
Preview how your page looks when shared on Twitter/X, LinkedIn, and Facebook.
Diff Checker
Compare two texts side by side with line numbers and character-level highlighting.
Code Line Counter
Paste code and count total, blank, comment, and code lines with a visual breakdown.
Emoji Picker
Search and copy emojis by name or keyword — with categories, recent history, and one-click copy.
Data Sanitizer
Remove or redact PII from text — emails, phone numbers, credit cards, IPs, API keys, and more.
File Metadata Viewer
View EXIF data, dimensions, GPS, magic bytes, and other metadata from any file.
Pomodoro Timer
Stay focused with a Pomodoro timer — 25 min work sessions, customizable breaks, session counter.
HTTP Request Tester
Send HTTP requests directly from your browser and inspect the response headers and body.
Text Reverser
Reverse characters, words, or lines — plus flip text upside-down and check palindromes.
Countdown Timer
Count down from a custom duration or to a specific future date and time.
DNS Lookup
Query DNS records (A, AAAA, MX, CNAME, TXT, NS, SOA) for any domain via Google DNS-over-HTTPS.
IP Geolocation
Instantly look up the location, ISP, timezone, and ASN for any IP address — or detect your own.
Code & pattern testers
- Regex Tester — test regular expressions with live match highlighting, capture group display, and global/case-insensitive flags.
- CRON Expression Tester — validate cron expressions and preview the next 10 scheduled run times in human-readable format.
- Semver Validator — parse and validate SemVer 2.0 strings (MAJOR.MINOR.PATCH), check pre-release tags, and compare two versions.
- JSON Path Tester — query JSON data with JSONPath expressions and inspect matching nodes.
- Diff Checker — compare two text blocks side by side with character-level diff highlighting and line numbers.
Security & analysis tools
- Password Strength Checker — analyze entropy, character variety, and estimated crack time for any password.
- HTTP Status Reference — quick reference for all HTTP 1xx–5xx status codes with descriptions and common use cases.
- IP Subnet Calculator — compute network address, broadcast address, host range, and CIDR notation for any IPv4 subnet.
- Chmod Calculator — convert Unix file permissions between symbolic (rwxr-xr-x) and numeric (755) representations.
- Color Contrast Checker — check WCAG 2.1 AA and AAA contrast ratio for any foreground/background color pair.
Text analysis tools
- Readability Score — analyze text with Flesch-Kincaid, Gunning Fog, and SMOG readability indices to target the right audience.
- Word & Character Counter — count words, characters, lines, sentences, and estimated reading time for any text.
- Byte Size Calculator — compute the exact UTF-8 byte size of any string — useful for validating API payload limits.