Free tools for developers, founders & makers
73 free calculators, converters and generators: app maintenance cost, runway and churn, PDF and JSON utilities, SEO checks and color tools. No accounts, no watermarks, no ads. Each tool shows how it works out its answer.
Updated
Useful tools, without the dark patterns
Most online utilities hide rate limits behind signups, bury features behind paywalls, or run analytics on every keystroke. These don't.
No signup for the free tier
Click and go. No forms, no verification emails, no waiting for a confirmation link. Free tools work the second you land; an account is only needed for Pro features.
Stays in your browser
55 of our 73 tools run entirely in your browser. The rest use our server for the heavy lifting, and each tool page explains what happens to your data.
Zero ads, no Facebook pixel
No Facebook pixel. No affiliate links. No sneaky redirects. The tool pages are GA4-instrumented only for aggregate usage counts — nothing about what you paste.
Built from real work
Most of these started as something we needed on a client build or our own products: formatting JSON, decoding JWTs, checking contrast, pricing maintenance. Each page shows how its answer is worked out.
Plan and budget an app
Estimate what an app costs to keep running and write the brief a developer can quote from.
App Maintenance Cost Calculator
Estimate the monthly engineering hours and cost of maintaining your app from its platforms, releases and integrations, priced in ₹ and $. Assumptions shown.
Open toolApp Project Brief Generator
Answer a few questions and get a clear one-page app project brief: goals, users, first-release features, budget band and deadline. Copy, download or send it.
Open toolGoogle Maps API Cost Calculator
Estimate your monthly Google Maps Platform bill for map loads, geocoding, routes and places on the global or India price list, with each SKU's free usage.
Open toolLLM API Cost Calculator
Work out the cost per request and per month of an AI feature on OpenAI, Claude or Gemini models, from tokens in and out, caching and batch prices.
Open toolApp Store & Google Play Fee Calculator
See what Apple and Google keep from an app sale or subscription: 15% and 30% rates, small business programs, renewals after a year, and Play's new 2026 fees.
Open toolRazorpay Fee Calculator
Calculate Razorpay's payment gateway fee and the 18% GST on it for UPI, cards, netbanking, international cards and Amex, and the amount that reaches your bank.
Open toolStripe Fee Calculator
Calculate Stripe's card fee and your payout in the US, UK, UAE and India for domestic and international cards, or the price to charge to net a set amount.
Open toolS3 Storage Cost Calculator
Estimate a month of object storage on AWS S3, Cloudflare R2, Backblaze B2 and Wasabi: storage, requests and egress from each provider's published price page.
Open toolApp Store Character Limits
Check an app's name, subtitle, keywords and descriptions against the App Store and Google Play character limits before you submit, field by field.
Open toolFounder and SaaS numbers
Runway, churn and uptime, worked out from your own numbers with the formula shown.
Startup Runway Calculator
Work out your startup's monthly net burn and how many months of runway are left, with revenue growth and a planned hire included. Free, in your browser.
Open toolChurn Rate Calculator
Calculate customer churn, gross and net MRR churn, net revenue retention and the customer lifetime they imply, for a subscription app or SaaS. Free, private.
Open toolUptime & SLA Calculator
Turn an uptime percentage like 99.9% or 99.99% into the downtime it allows per day, week, month and year, or measured downtime back into uptime.
Open toolCustomer Lifetime Value Calculator
Work out customer lifetime value for a subscription business from revenue per customer, gross margin and churn, plus the LTV to CAC ratio.
Open toolCAC Payback Calculator
Calculate how many months it takes to earn back the cost of acquiring a customer, from CAC, revenue per customer and gross margin, with churn factored in.
Open toolEquity Dilution Calculator
See how a funding round dilutes founders: pre-money valuation, investment and a new option pool give the post-money ownership of each holder, round by round.
Open toolBreak-Even Calculator
Work out how many units, customers or subscriptions you need to sell to cover fixed costs, from price and variable cost per unit, with the margin of safety.
Open toolDeveloper utilities
Daily-use formatters, decoders, converters and calculators. Save a bookmark.
Markdown to PDF
Convert Markdown to a typeset PDF with code highlighting and LaTeX math. Free, no signup, no watermark.
Open toolJSON Formatter
Format, validate, minify, and auto-fix JSON in your browser. Fixes trailing commas, unquoted keys, single quotes, comments, and more.
Open toolBase64 Encoder / Decoder
Encode and decode Base64 text. Supports UTF-8, URL-safe variant, and line-wrapping.
Open toolUUID Generator
Generate v4 UUIDs (1 to 1000 at a time). Lowercase, uppercase, or brace-wrapped. Copy or download.
Open toolRegex Tester
Test regular expressions with flags (g, i, m, s, u, y). Live match highlighting, capture groups, flag reference.
Open toolCase Converter
Convert text between snake_case, camelCase, PascalCase, kebab-case, CONSTANT_CASE, Title Case, and more.
Open toolURL Encoder / Decoder
Percent-encode and decode URL components. Full-URL mode preserves scheme and host; component mode escapes reserved chars.
Open toolHTML to PDF
Convert raw HTML (or paste-in webpages) to a typeset PDF. Custom CSS, A4 / Letter, syntax-highlighted code, perfect tables.
Open toolPDF Merger / Splitter
Combine multiple PDFs in any order, or extract specific page ranges. Up to 100 files on Pro+. Privacy-first, files are never persisted.
Open toolPDF Compressor
Shrink PDF filesize without quality loss. Picks the most efficient encoding. Up to 100 MB on Pro+.
Open toolCSV ↔ JSON Converter
Convert CSV (with headers, custom delimiters) to JSON, or JSON arrays back to CSV. Type-aware parsing, error reporting.
Open toolYAML ↔ JSON Converter
Convert YAML to JSON or JSON to YAML. Useful for Kubernetes manifests, GitHub Actions, OpenAPI specs.
Open toolJSON to TypeScript
Generate TypeScript interfaces from a JSON sample. Powered by quicktype, prefers unions, accurate optional inference.
Open toolJSON Validator & Diff
Validate JSON against a JSON Schema, or diff two JSON documents and see exactly what changed. Per-field reports.
Open toolMarkdown Table Editor
Paste CSV or TSV, get a perfect Markdown table back. Per-column alignment, escapes pipes and newlines for you.
Open toolCron Expression Generator
Convert cron syntax to plain English, validate, and preview the next 5 fires in your timezone. Supports 5- and 6-field cron.
Open toolGitHub README Generator
Generate a clean README.md from a few inputs: project name, tagline, features, tech stack, install + usage. Copy-paste ready.
Open toolUnix Timestamp Converter
Convert a Unix epoch timestamp in seconds or milliseconds to a date in UTC, IST and your own time zone, or a date back to epoch time. Detects the unit for you.
Open toolChmod Calculator
Convert Linux file permissions between octal like 755, symbolic like rwxr-xr-x and the chmod command, with owner, group and other access explained.
Open toolSubnet Calculator
Enter an IPv4 address with a CIDR prefix such as 192.168.1.10/24 to get the network, broadcast, netmask, wildcard mask, usable host range and host count.
Open toolSHA-256 Hash Generator
Generate a SHA-256, SHA-384, SHA-512 or SHA-1 hash of any text as hex or Base64, computed by your browser's Web Crypto API. Your text is never sent to a server.
Open toolHTML Entity Encoder
Encode text into HTML entities so it shows safely in a web page, or decode named, decimal and hex entities back into characters. Runs in your browser.
Open toolNumber Base Converter
Convert numbers between binary, octal, decimal and hexadecimal, or any base from 2 to 36, with large numbers kept exact and the working shown.
Open toolData Size Converter
Convert bytes, KB, MB, GB and TB in both decimal (1,000) and binary (1,024) units, and see why a 1 TB drive shows up as about 931 GiB. Runs in your browser.
Open toolHTTP Status Codes
Look up any HTTP status code, from 200 OK to 503 Service Unavailable: what it means, where it is defined, and when an API should return it. Full list included.
Open toolMIME Type Lookup
Find the MIME type for a file extension, or the extensions for a MIME type, checked against IANA's registry: the Content-Type header your server should send.
Open toolDiff Checker
Paste two versions of a text or code file and see every added, removed and changed line, with word-level changes marked. Runs in your browser.
Open toolJSON Escape
Escape text so it can sit inside a JSON string, quotes, backslashes, newlines and control characters included, or unescape a JSON string back into plain text.
Open toolString Length Calculator
Count a string's characters, Unicode code points, UTF-8 and UTF-16 bytes, words and lines, and why an emoji is one character but two JavaScript units.
Open toolIP to Binary Converter
Convert an IPv4 address to binary, decimal and hexadecimal, or binary back to dotted decimal, with each octet's working shown. Runs in your browser.
Open toolUser Agent Parser
Paste a User-Agent string to read the browser, version, operating system, rendering engine and device type, with notes on what modern browsers no longer send.
Open toolAndroid API Levels
Every Android version with its API level, codename where it has one and release year, plus the target API level Google Play requires. Look up any level.
Open toolSEO and marketing
Check how a page looks in Google, write robots.txt and tag campaign links.
SERP Snippet Preview
Preview your page as a Google result and check the title's pixel width and meta description length against our budgets: 600 px and 120–160 characters.
Open toolRobots.txt Generator
Build a robots.txt file: allow or block crawlers, disallow paths, add your sitemap and choose a rule for each AI crawler such as GPTBot and ClaudeBot.
Open toolUTM Builder
Build a campaign link with utm_source, utm_medium, utm_campaign, utm_term and utm_content, checked for common tagging mistakes, then copy it.
Open toolURL Slug Generator
Turn a title into a clean URL slug: lowercase, hyphens, accents and symbols removed, with optional stop-word trimming and a length cap. Runs in your browser.
Open toolMeta Tag Generator
Generate the title, meta description, canonical, Open Graph and Twitter card tags for a page, checked against the length budgets we use, ready to paste.
Open toolSchema Markup Generator
Generate JSON-LD for an organization, a local business, breadcrumbs, a FAQ page, an article or a software app, using schema.org types, ready to paste.
Open toolSecurity & auth
Password generation and JWT inspection — both run entirely in your browser.
Design & assets
Colors, contrast, sizes, QR codes and favicon bundles.
QR Code Generator
Generate QR codes for URLs, Wi-Fi, contact cards, or plain text. Custom colors and error-correction levels.
Open toolDynamic QR Codes
QR codes you can edit anytime — change destination URL without reprinting. Track scans by date, country, device. Pro feature.
Open toolColor Palette Generator
Generate harmonious color palettes from a seed color. Monochrome, analogous, complementary, triadic, and tetradic schemes.
Open toolFavicon Generator
Upload an image and get a ZIP with favicon.ico, all PNG sizes, Apple touch icon, site.webmanifest, and a paste-ready HTML snippet.
Open toolImage Compressor
Compress JPG, PNG, WebP, AVIF without visible quality loss. mozjpeg encoder. Resize on the fly.
Open toolImage Format Converter
Convert between JPG, PNG, WebP, and AVIF. mozjpeg encoder for smallest JPGs. Free with sensible daily limits.
Open toolImage Background Remover
AI background removal — strip the backdrop from any photo and download a transparent PNG. Pro+ feature.
Open toolOG Image Generator
Generate 1200×630 social-share images from a title + subtitle. 3 templates, custom colors. Free with limits.
Open toolSVG Optimizer
Minify SVG files via svgo. Strips IDs, comments, redundant attributes. Often shaves 30-70% off filesize.
Open toolPX to REM Converter
Convert pixels to rem and rem to pixels for any root font size, with a CSS line to copy and a table of common sizes from 10 to 64 px. Runs in your browser.
Open toolHEX to RGB Converter
Convert a HEX color code to RGB, RGBA and HSL, or an rgb() value back to HEX, with a live swatch and CSS to copy. Handles 3, 4, 6 and 8-digit HEX codes.
Open toolColor Contrast Checker
Check the contrast ratio between a text color and a background against WCAG 2.2 AA and AAA, for normal and large text, and get the nearest shade that passes.
Open toolAspect Ratio Calculator
Find the aspect ratio of any width and height, or the missing side for a ratio like 16:9 or 4:3, with the CSS aspect-ratio value and common screen sizes.
Open toolCSS Box Shadow Generator
Build a CSS box-shadow with offset, blur, spread, color and opacity, layer up to three shadows, preview it live, and copy the CSS or a Tailwind arbitrary value.
Open toolCSS Gradient Generator
Create a linear, radial or conic CSS gradient from two to four color stops, preview it live, and copy the background CSS with a solid-color fallback.
Open toolApp Icon Sizes
The app icon sizes Apple and Google ask for: the 1024 px App Store icon, the 512 px Play icon, Android launcher sizes and adaptive layers, with a size checker.
Open toolApp Store Screenshot Sizes
The screenshot sizes and counts the App Store and Google Play accept, by device, with a checker that tells you whether your image's dimensions will upload.
Open tool