Full site index — all free developer, image & SEO tools
Privacy-first, browser-based tools — no mandatory upload, no signup on most pages. Jump to a hub or browse every indexed tool below.
Hubs & landing pages
Developer tools hub
Index of all in-browser developer utilities and language hubs.
JSON tools hub
Format, validate, minify, and convert JSON.
HTML tools hub
HTML format, minify, validate, and convert.
XML tools hub
XML format, validate, minify, and convert.
JavaScript tools hub
JS format, minify, validate, and convert.
AI & LLM tools hub
Token counters, LLM cost calculators, RAG math, and more.
Developer utilities hub
Regex, JWT, cron, UUID, diff, QR, Base64, Markdown, and more.
Creative tools hub
Image compression, upscaling, color tools — browser-first.
Image tools hub
Compressor, upscaler, background removal, and related image tools.
Design tools hub
Color conversion, contrast checking, and design utilities.
SEO tools hub
Meta tags, JSON-LD helpers, and sitemap generators.
SaaS & founder tools hub
MRR, fees, runway, and subscription metrics.
Home & DIY hub
Concrete and practical home project calculators.
Converters landing
Data format converters and transforms.
Guides
Editorial guides and tutorials.
Comparisons
Tool and format comparison pages.
Developer tools
AI Token Counter (GPT, Claude, Gemini)
Count tokens with o200k-style tokenization, then compare estimated LLM API cost across 30+ models. Pairs with the per-token cost calculator; all in-browser.
API rate limit checker
TPM and RPM headroom against illustrative dev/production tiers.
Audio API cost estimator
Duration-based illustrative cost bands for speech and TTS-style workloads.
Base64 encode / decode
Standard and URL-safe Base64; text and small file drops — client-side only.
Context window visualizer
Prompt + history size vs model context with 70% / 90% markers.
Cron Expression Builder & Generator
Free online cron builder: translate schedules to plain English, validate syntax, and preview next runs.
Diff Checker
Online diff checker tool — compare CSV, XML exports, or text side-by-side with line-level highlighting.
Discord Timestamp Converter
Generate Discord dynamic t: timestamps from Unix epoch — copy default, full, relative, time, or date styles.
Embedding cost calculator
Float32 GB estimate plus embedding API math for ingest and monthly queries.
Fine-tune vs prompt calculator
Break-even requests after a one-time fine-tune fee using your $/M assumptions.
HTML Converter
Convert HTML entities or transform HTML to JSX/Markdown.
HTML Formatter
Beautify HTML code with proper indentation.
HTML Minifier
Compress HTML by removing whitespace and comments.
HTML Validator
Check HTML for syntax errors and standard compliance.
JS Converter
Convert between JavaScript versions or transform to/from TypeScript.
JS Formatter
Beautify and format JavaScript code with proper indentation.
JS Minifier
Compress JavaScript code by removing whitespace and unnecessary characters.
JS Validator
Check JavaScript code for syntax errors and quality issues.
JSON Converter
Convert JSON data to XML, YAML, CSV, or HTML formats.
JSON Formatter
Pretty-print JSON, mask likely secrets, and copy bash cURL or Postman import — for webhooks and API payloads.
JSON Validator
Validate JSON syntax and structure against schemas.
JWT Debugger
Decode, inspect, and verify JSON Web Tokens with HMAC signature checking.
LLM API cost (per token count)
Enter input and output token counts; compare price across 30+ models. Deep-links from the token counter; cache- and reasoning-aware.
LLM model comparison (2–4 models)
Side-by-side matrix: context, API $/M, capabilities; shareable ?models= links. Pairs with token counter and cost calculator.
LLM pricing changelog
Editorial log of llm-pricing.json updates; pairs with /feed/pricing.xml.
LLM scenario planner
Users × requests/day × tokens with ×2/×5 stress and 12‑month projection for one reference model.
Markdown to HTML
MD → HTML with email-safe mode, optional changelog wrap, scripts stripped in-browser.
Number to Words Converter
Number to words online, A1Z26 letter–number cipher, and phone keypad vanity mapping — all in your browser.
Password Generator
Generate strong, random passwords and passphrases with a live entropy score.
Prompt caching calculator
Compare per-request cost with and without prompt cache hits using published cached-input rates.
QR code generator
Create QR codes for URLs, text, Wi‑Fi, and vCard — PNG download, error correction, colors.
RAG cost simulator
Documents × chunks × top‑K × daily queries × output tokens — illustrative monthly LLM spend.
Regex Tester
Regex tester online with Go RE2, bash/grep, sed -E, Perl, and C# flavor guides — live matches in your browser.
Timestamp Converter
Convert between Unix epoch timestamps and human-readable dates across time zones.
UUID / ULID / NanoID Generator
Generate secure UUID v4, ULID, and NanoID identifiers in bulk.
Vision token estimator
Rough planning estimate for image width/height → vision tokens.
XML Converter
Convert XML data to JSON, YAML, or CSV formats.
XML Formatter
Beautify and format your XML code for readability.
XML Minifier
Compress XML by removing unnecessary whitespace.
XML Validator
Check XML for well-formedness errors.
Creative & image tools
Background Remover
Remove backgrounds from images instantly using AI.
Color Contrast Checker
Check WCAG AA/AAA contrast ratios for any foreground/background color pair.
Color Converter
Convert colors between HEX, RGB, HSL, and CMYK formats.
Image Compressor
Reduce image file sizes while maintaining quality.
Image Upscaler
Upscale images 2x to 16x with high-quality interpolation, entirely in your browser.
SEO tools
JSON-LD SaaS pack (Product + FAQ + Org)
Build Organization, Product, and FAQPage JSON-LD in one copy-paste block for landing pages.
Meta Tag Generator
Generate comprehensive, SEO-friendly meta tags for your website.
Sitemap.xml Generator
Build sitemap.xml from path lists or CSV (optional lastmod) for Next.js, Vite, and SPAs.
SaaS & founder tools
Burn rate & runway
Cash in bank, monthly net burn, runway months — pairs with MRR/ARR and founder planning content.
MRR & ARR from CSV
Paste a subscription CSV, sum MRR, see ARR — for ops and light finance checks in the browser.
SaaS Tools hub
MRR/ARR, fees, LTV/CAC, runway — B2B SaaS subscription metrics in the browser.
SaaS unit economics (LTV, CAC, churn, payback)
Subscription LTV, LTV:CAC, CAC payback from ARPA, margin, and monthly churn — labels avoid loan/mortgage intent.
Stripe & PayPal fee (take-home)
Estimate card fees and net after simplified Stripe or PayPal-style pricing (not official rates).
Home & DIY calculators
Why use this index?
Fast internal links
Surface long-tail tools (JWT, cron, RAG calculators) without relying on off-site search alone.
Privacy angle
Most utilities run fully in your browser — check each page for the exact network behavior.
Always expanding
The list is driven from the same catalog as the site navigation so new tools appear here automatically.