Free tools for engineers who ship.

One URL in, one report out: SEO, social previews, security headers, performance, crawlability and AI search readiness, scored with fixes.

Grade any site's HTTP security headers from A to F, then build a Content Security Policy with copy-ready snippets for Next.js, Vercel, Nginx and Apache.

Can ChatGPT, Claude, Perplexity and Gemini read and cite your site? Check AI crawler access, llms.txt, structured data and server-rendered content.

Create a valid llms.txt for your website in minutes. Import pages from your sitemap, group them into sections and download the file.

Paste a prompt to count tokens, then compare the cost and context fit of Claude, GPT and Gemini models per request, per day and per month.

Generate row-level security policies for Supabase and Postgres: public, signed-in, owner-only, team and admin access, with the indexes and explanations.

Build a clean GitHub profile README with your intro, skills badges, links and stats cards. Import your profile, preview it live and copy the Markdown.

Write flowcharts, sequence, ER, class and architecture diagrams as text, preview them live and export crisp SVG or PNG for docs and slides.

Turn code into a beautiful, shareable image for LinkedIn, X and slides, with real syntax highlighting, themes, window chrome and 2× export.

Find a meeting time that works across time zones. Compare working hours side by side and share the slot as a calendar link or .ics file.

Generate a perceptually even 50–950 colour scale from one brand colour, in OKLCH, with Tailwind v4 @theme tokens, CSS variables and contrast checks.

Generate fluid font sizes and spacing with CSS clamp(). Set the minimum and maximum, preview across screen widths and build a full type scale.

Create every favicon and app icon you need from one image, emoji or letter: favicon.ico, Apple touch icon, PWA and maskable icons, manifest and HTML.

Shrink SVG files with SVGO without visible changes. Compare before and after, then copy the markup, a data URI or a React component.

Convert and compress images to WebP, AVIF, JPEG or PNG in bulk. Resize, set the quality, compare sizes and download them all as a zip.

Sign a PDF in your browser: draw, type or upload your signature, place it on any page, add the date and download. Nothing is uploaded.

Combine several PDF files into one, in the order you choose. Fast, free and private: the files never leave your device.

See every page of a PDF, then reorder, rotate, delete, extract or split pages and download the result. Free and private.

Turn Markdown into a clean, well-typeset PDF for technical docs, proposals and reports, with code highlighting, tables and print-ready themes.

Paste or open a table in any format and convert it to CSV, Excel, JSON, Markdown, LaTeX, HTML or SQL inserts, with a live preview.

Type a LaTeX equation and export it as a crisp SVG or transparent PNG for reports, slides and papers. Includes a symbol palette and templates.

Generate subtitles from any video or audio with Whisper AI running in your browser. Edit the captions, shift the timing and export SRT or VTT.

Convert length, force, pressure, energy, power, torque, flow, temperature and more, with significant figures and engineering notation.

Decode 4, 5 and 6-band resistor colour codes, or find the bands for any value, snapped to the nearest E12, E24 or E96 standard value.

Solve voltage, current, resistance and power from any two values, combine series and parallel resistors and design voltage dividers and LED resistors.

Calculate voltage drop for copper and aluminium cables in DC, single-phase and three-phase circuits, in mm² or AWG, and find the smallest cable that passes.

Analyse simply supported and cantilever beams with point loads and distributed loads. Get reactions, shear and bending moment diagrams and deflection.

Paste CSV data and make clean line, scatter, bar and area charts for reports and papers. Export sharp SVG or high-resolution PNG.

Plan a project timeline in minutes: add tasks, phases, dates and progress, then export the Gantt chart as SVG or PNG, or save the data as CSV.

Add text, images, logos, boxes and highlights to any PDF, or white out what shouldn't be there. Free, no sign-up, and the file never leaves your device.

Stamp a text or logo watermark across every page and add page numbers in any position and format, with a live preview. Free and private.

Shrink large PDFs, especially scans, for email and upload portals. Choose how much to compress and see the new size before you download.

Turn every PDF page into a PNG or JPG at screen or print resolution, or combine photos and scans into one PDF. Free, no watermark.

Make a clean, professional invoice, quotation or receipt in any currency, with your logo, tax and bank details. Download a PDF or PNG. No sign-up, no watermark.

Work out personal income tax in Sri Lanka from local and foreign-currency income, with the Rs 1.8M relief, the 6% to 36% slabs and the 15% cap on foreign income.

See the APIT (PAYE) deducted from a monthly salary in Sri Lanka, your take-home pay and the yearly total, using the rates from 1 April 2025.

Add VAT or GST to a net price, or take it out of a gross price. Presets for Sri Lanka, India, UK, Australia, New Zealand, Singapore and the UAE, or any rate.

Know how much of every payment to put aside for tax as a freelancer. Uses Sri Lanka's rules automatically, or your own rate anywhere else.

Turn cost and price into margin and markup, find the price for a target margin, and see how many sales you need to break even.

Build a depreciation schedule for any asset with straight-line, declining-balance or sum-of-years methods, and export it to CSV.

Find the monthly payment on a home, car or personal loan, the total interest, and how much an extra monthly payment saves. Includes a yearly schedule.

See how savings grow with compound interest and monthly deposits, in today's money after inflation, or find what to save each month to reach a goal.

Plan a monthly budget line by line and check it against the 50/30/20 rule for needs, wants and savings. Saved in your browser only.

List your debts and see how fast you can be debt-free with the avalanche or snowball method, and how much interest each one saves.

Find your financial independence number and when you'll reach it, from your savings, monthly investing, spending and expected returns, in today's money.

See the payback, return and savings of rooftop solar. Uses Sri Lanka's 2026 CEB tariff and Net Plus rates, or your own tariff anywhere in the world.