Developer tools
JSON, regex, JWT, hashes, colors, CIDR and cron — the daily-driver utilities, processed in your browser so your data stays yours.
Most popular
Base64 / URL / HTML Encoder-Decoder
Encode and decode Base64, hex, URL percent-encoding and HTML entities — with auto-detect, bulk lines and file drop.
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CSS Gradient, Shadow & Radius Generator
Visual generators for gradients, box-shadows and border radii.
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Color Converter & Contrast Checker
HEX ↔ RGB ↔ HSL ↔ OKLCH, plus WCAG contrast ratios.
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Cron Expression Parser
Explain any cron expression and preview its next runs.
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Crontab Builder
Build a cron expression with dropdowns, no syntax needed.
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Flowchart & Diagram Editor
Draw flowcharts with shapes, arrows and labels; export SVG or PNG.
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HTML & JS Playground
Write HTML, CSS and JavaScript with a live preview and console.
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Hash Generator
MD5, SHA-1/256/384/512, CRC32, file checksums, bcrypt and digest compare.
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JSON Formatter & Validator
Format, validate, minify and query JSON with JSONPath.
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JSON Schema Validator
Validate JSON data against a JSON Schema.
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JSON ↔ YAML ↔ TOML ↔ XML ↔ CSV
Convert between the five common data formats.
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JWT Decoder
Decode JWT header and payload, check expiry — locally.
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Python Playground
Run Python with numpy, pandas and matplotlib in your browser.
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Regex Tester
Test regular expressions live, with a plain-English explanation.
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SQL Formatter
Pretty-print and minify SQL for any major dialect.
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Subnet / CIDR Calculator
Network, broadcast, host range and mask from CIDR notation.
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URL Parser & Query Editor
Split a URL into parts and edit query parameters in a table.
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UUID / ULID / Nano ID Generator
Generate UUID v4/v7, ULID and Nano ID — in bulk.
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Unix Timestamp Converter
Unix time ↔ human date, any unit, any timezone.
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curl Converter
Turn a curl command into fetch, axios, Python or PowerShell.
JSON & Code
JSON Formatter & Validator
Format, validate, minify and query JSON with JSONPath.
popular
JSON Schema Validator
Validate JSON data against a JSON Schema.
popular
JSON ↔ YAML ↔ TOML ↔ XML ↔ CSV
Convert between the five common data formats.
popular
Regex Tester
Test regular expressions live, with a plain-English explanation.
popular
SQL Formatter
Pretty-print and minify SQL for any major dialect.
.gitignore Generator
Build a .gitignore from language, IDE, and OS templates with deduplication, stack presets, and share links.
JSON Diff
Structural diff of two JSON documents.
Mock JSON Generator
Generate fake API responses from a JSON template.
String Escaper
Escape and unescape JSON, shell, regex, SQL, CSV, and HTML text with a live before→after preview.
YAML Linter
Validate YAML and see the exact error line.
Encoding & Hashing
Base64 / URL / HTML Encoder-Decoder
Encode and decode Base64, hex, URL percent-encoding and HTML entities — with auto-detect, bulk lines and file drop.
popular
Hash Generator
MD5, SHA-1/256/384/512, CRC32, file checksums, bcrypt and digest compare.
popular
JWT Decoder
Decode JWT header and payload, check expiry — locally.
HMAC Calculator
HMAC-SHA256/512/1/MD5 with text or hex inputs, hex + Base64 output, and timing-safe verify.
String Length Inspector
Characters, UTF-8 bytes, UTF-16 units and graphemes of any text.
Byte Size Converter
Convert between KB, KiB, MB, MiB and friends.
Web & CSS
CSS Gradient, Shadow & Radius Generator
Visual generators for gradients, box-shadows and border radii.
popular
Color Converter & Contrast Checker
HEX ↔ RGB ↔ HSL ↔ OKLCH, plus WCAG contrast ratios.
popular
URL Parser & Query Editor
Split a URL into parts and edit query parameters in a table.
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curl Converter
Turn a curl command into fetch, axios, Python or PowerShell.
HTTP Status Codes
Search by code, phrase, or symptom — with retry/cache badges, causes, fixes, and RFC links.
Keycode Inspector
Press any key, see event.key, event.code and modifiers.
User-Agent Parser
Decode any user-agent string: browser, engine, OS, device.
HTML Entity Reference
Search, filter and copy HTML entities — with encode/decode.
MIME Type Lookup
File extension ↔ MIME type, in both directions.
Time & IDs
Cron Expression Parser
Explain any cron expression and preview its next runs.
popular
Crontab Builder
Build a cron expression with dropdowns, no syntax needed.
popular
UUID / ULID / Nano ID Generator
Generate UUID v4/v7, ULID and Nano ID — in bulk.
popular
Unix Timestamp Converter
Unix time ↔ human date, any unit, any timezone.
ID Decoder (UUID, ULID, ObjectId, Snowflake)
Auto-detect ID format; decode timestamps in bulk.
Epoch Millis vs Seconds Detector
Paste a numeric timestamp, learn its unit and value.
Network & System
Subnet / CIDR Calculator
Network, broadcast, host range and mask from CIDR notation.
Chmod Calculator
Octal ↔ symbolic Unix permissions, with checkboxes.
DNS Lookup
A, AAAA, MX, TXT, NS, CNAME records via DNS-over-HTTPS.
SSL Certificate Decoder
Paste a PEM certificate, see subject, issuer, SANs, validity.
WHOIS Lookup
Registrar, dates and nameservers of any domain.
MAC Address Lookup
Vendor (OUI) lookup plus the meaning of every MAC bit.
Algorithms & CS
Bloom Filter Playground
Add items, watch bits light up, measure the false positive rate.
Cache Replacement Simulator
Animate FIFO, LRU, LFU, CLOCK, ARC and Bélády's OPT on any access sequence.
Consistent Hashing Ring
See why adding a server moves 1/N of the keys, not all of them.
Data Structure Visualizer
Watch BST, AVL, red-black trees, heaps, hash tables, tries and union-find work, step by step.
Digital Logic Gate Simulator
Build circuits from gates and flip-flops, wire them up, and watch the signals flow live.
Git Branching Sandbox
Type git commands and watch the commit DAG, branches and HEAD move — with levels, remotes, undo, and merge-vs-rebase contrast.
IEEE-754 Floating Point Explorer
Flip the bits of a float and see why 0.1 + 0.2 ≠ 0.3.
Karnaugh Map Minimizer
Minimize boolean functions on a K-map with don't-cares and grouped prime implicants.
Raft Consensus Visualizer
Watch leader election, log replication and network partitions in a live Raft cluster.
Regex Backtracking Visualizer
Watch catastrophic backtracking explode, step by step.
Tail Latency & Autoscaling Simulator
See p99 explode past 80% utilization — and retries make it worse.
Playgrounds & Diagrams
Flowchart & Diagram Editor
Draw flowcharts with shapes, arrows and labels; export SVG or PNG.
popular
HTML & JS Playground
Write HTML, CSS and JavaScript with a live preview and console.
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Python Playground
Run Python with numpy, pandas and matplotlib in your browser.
LaTeX Equation Editor
Type LaTeX, see the rendered formula live; export SVG or PNG.
About these tools
Developer utilities without the clutter: JSON and SQL formatters, Base64 and URL encoding, regex testing, hash generation, UUIDs, JWT decoding, timestamp conversion and color pickers. Everything runs client-side, so tokens, credentials and snippets stay on your machine.