Free developer tools
Small, single-purpose utilities for jobs that are otherwise done by hand. Each one runs entirely in your browser: nothing you paste is uploaded, stored, or sent to a server.
AI & LLM
-
OpenAI Structured Outputs JSON Schema Converter
Paste any JSON Schema and get one OpenAI accepts with strict: true — additionalProperties, required and unsupported keywords fixed everywhere, plus ready-to-run Python and TypeScript.
-
Openai Fine Tuning Jsonl Validator
Moderate-to-high niche search volume driven by developers getting opaque validation errors when submitting OpenAI fine-tuning jobs.
-
Markdown Text Chunker for RAG
High and growing developer search intent for client-side RAG preprocessing tools as engineers optimize Markdown context retrieval for LLM vector embeddings.
-
LLM Vision Token Calculator
Image input tokens for GPT-4o, GPT-4.1, o-series, Claude and Gemini from pixel size, with OpenAI’s 512px tile grid drawn and a cost comparison.
-
Custom GPT Action Schema Validator
Check an OpenAPI schema against the GPT action builder: operationIds, servers, length limits, missing properties and items, auth. Auto-fix included.
-
Prompt XML Tag Sanitizer
Escape untrusted text before wrapping it in XML tags in an LLM prompt, so it cannot close the tag and pose as instructions. With Python, JS and Go code.
App Store & ASO
-
App Store Keyword Field Deduplicator
Strip words Apple already indexes from your app name, subtitle and categories, fold plural duplicates, and see exactly how much of the 100-character keyword field you just got back.
-
App Icon Squircle Mask Previewer
See an app icon under the iOS continuous-corner squircle, macOS, Google Play and Android adaptive masks, with safe zones and an automatic safe-zone check.
Audio & Podcasting
-
ACX Audio Spec Checker
Check an audiobook chapter against ACX requirements in your browser: RMS, peak, noise floor, 192 kbps CBR, 44.1 kHz and room tone, with the fix for each.
CAD & Fabrication
-
Gcode to SVG Converter
Strong niche search intent from CNC machinists, laser engraver users, and pen plotter hobbyists needing to reverse-engineer toolpaths into scalable 2D vector graphics.
Developer Utilities
-
Log4j Pattern to Regex Converter
Steady developer demand from Java devs and DevOps engineers needing to parse legacy Log4j/Logback log formats into SIEMs, Logstash, or custom regex parsers.
-
Cron to AWS EventBridge Cron Converter
Paste a Linux cron line, get a valid EventBridge cron(): day of week renumbered, the ? rule applied, either-or schedules split, plus CLI, Terraform and CDK.
-
W3C Traceparent Header Parser
Split a traceparent into version, trace ID, span ID and flags, validate it against the Trace Context spec, parse tracestate, and generate valid headers to test with.
-
Postgres DDL to Mermaid Converter
Paste CREATE TABLE or pg_dump output and get a Mermaid ER diagram with keys marked and cardinality derived from NOT NULL, UNIQUE and primary keys.
-
Manifest V3 Permission Checker
Paste a Chrome extension manifest.json to see the exact install warnings Chrome shows, catch Manifest V3 errors and convert V2 manifests to V3.
-
HAR to k6 Converter
Turn a browser HAR recording into a k6 load test script, with static assets and trackers filtered out, redirects handled and tokens moved to __ENV.
-
WebAuthn AAGUID Lookup
Find which passkey provider or security key an AAGUID belongs to, or paste a registration response to decode its AAGUID, flags and public key.
-
XML Formatter
Format, validate and minify XML online: 2, 4 or tab indents, errors by line and column, and text kept exactly as written.
-
JSON Formatter
Format, validate, minify and repair JSON: errors by line and column, sorted keys, and big numbers kept exactly as written.
-
UUID Generator
Generate v4 random, v7 time-ordered, v1 and v5/v3 name-based UUIDs in bulk and any format, and decode any UUID’s version and timestamp.
-
JWT Decoder
Decode a JWT’s header and payload, see every claim explained and expiry as a real date, and verify its signature with a secret, PEM or JWK.
Etsy & Marketplaces
-
Etsy Tag 20 Character Limit Tool
Paste tags that blow Etsy's 20-character limit and get them repacked on word boundaries — your words, your order, never cut mid-word — with the 13-slot count and a line ready for the listing editor.
Logistics & Shipping
-
Ti Hi Pallet Calculator
Cases per layer, layers high and cases per pallet, with mixed layer patterns that beat block stacking, a drawn layer and a printable staging sheet.
Print & Design
-
Image DPI to Print Size Calculator
Drop an image to see every size it prints at 300, 240 and 150 DPI, how 18 standard frames crop it, and the upscale needed to reach 300 DPI.
Social Media
-
Bluesky Rich Text Facet Calculator
Correct UTF-8 byte offsets for Bluesky mentions, links and hashtags, Markdown links converted, and a ready-to-send app.bsky.feed.post record.
Students & Grades
-
GPA Calculator
Weighted and unweighted GPA for high school and college, from letters or percentages, with cumulative GPA and the GPA you need next term.
-
Final Grade Calculator
The score you need on your final exam for an A, B, C or D, what-if results for any final score, and your current grade from weighted categories.
Video & Subtitles
-
Spatial Video Metadata Viewer
Niche but rapidly growing search volume driven by Apple Vision Pro and Meta Quest creators troubleshooting stereoscopic MV-HEVC video encoding and metadata tags.
-
SRT to YouTube Chapters
Turn an .srt subtitle file into a YouTube chapter list — first chapter forced to 0:00, which YouTube silently requires, plus a check against its three-chapter and ten-second rules.
Work & Time
-
Time Card Calculator
Weekly hours from clock-in and out times minus lunch breaks, with federal or California overtime, decimal hours, gross pay and a CSV download.
Writing & Readability
-
Fry Readability Graph Calculator
Steady search volume from US K-12 teachers, curriculum authors, and publishers requiring official Fry grade-level verification.
-
Obsidian Callout to GitHub Alert Converter
Convert Obsidian callouts to GitHub’s five alerts: every type and alias mapped, titles moved so GitHub still renders them, folding handled, code blocks untouched.
-
Text Compare
Compare two texts and see every difference: side-by-side or inline, changed words highlighted, ignore whitespace or case, and a patch to download.
-
Lorem Ipsum Generator
Placeholder text by paragraphs, sentences, words, list items or an exact character limit, as plain text, HTML or Markdown.
-
Case Converter
Convert text to UPPERCASE, lowercase, AP-style Title Case, Sentence case, camelCase, snake_case, kebab-case and more, all at once.
-
Word Counter
Count words, characters, sentences and reading time as you type, with keyword density and exact limits for X, SMS, Google, Instagram and LinkedIn.
Looking for written comparisons instead? Read the software reviews.