Free online tools that never upload your data.
Every tool runs 100% in the browser — no processing servers, no sign-up, works offline.
A project by Synth88 Labs Inc. · Live at lazytools.io since July 4, 2026.
Every day, millions of people upload private files — contracts, photos, IDs — to "free online tools" websites, trusting a stranger's server in exchange for a simple conversion. That trade never made sense to us. Modern browsers can do this work locally.
LazyTools is built on one non-negotiable principle: privacy by architecture, not by policy. There are no processing servers. The tool code downloads to your device and runs there. You can verify it yourself: open DevTools, watch the network tab, or switch off your connection mid-use — everything keeps working.
| Category | Highlights |
|---|---|
| Unit Converters | 27 quantities — length, weight, temperature, volume, area, speed, time, data storage, pressure, energy, power, data-transfer-rate (Mbps↔MB/s), frequency (Hz/RPM/rad·s), torque (N·m↔lbf·ft), force (N/lbf/kgf), density, volumetric flow-rate (L/min↔GPM), angle (deg/rad/gon/arcmin/arcsec), acceleration (m/s²/g/ft-s²), illuminance (lux/foot-candle), magnetic field (tesla/gauss), dynamic viscosity (Pa·s/poise/cP), kinematic viscosity (m²/s/stokes/cSt), radioactivity (becquerel/curie), luminance (nit/cd·m²/foot-lambert), electric charge (coulomb/Ah/mAh), typography (point/pixel/pica, 96px=72pt) — exact NIST/BIPM factors (audited by verify-factors.ts), per-pair editorial notes |
| Calculators | 29 tools — percentage, EMI, BMI, age, tip, discount, interest, mortgage, sales tax, fuel cost, GPA, test grade (EZ grader), unit price, overtime pay, square footage, cost per square foot, dilution ratio (1:N mixing)… |
| Finance | 22 tools — NPV & IRR (discounted cash flow, bisection IRR), debt-to-income (DTI) (front/back-end + lender bands), inflation (real value + purchasing-power loss), compound interest (FV with regular contributions + growth chart), debt payoff (snowball vs avalanche, month-by-month, payoff-order table), savings goal, loan payoff (amortization + extra-payment savings), credit-card payoff (time or payment), CAGR, ROI (+ annualized), rule of 72, break-even units, APR↔APY, plus 6 financial-ratio calculators — liquidity (current/quick/cash/working capital), leverage (D/E, debt ratio, equity multiplier), coverage (interest coverage/TIE, DSCR, fixed-charge), profitability (gross/operating/net margin, ROA, ROE), efficiency (turnover, DSO/DPO, cash conversion cycle), valuation (P/E, P/B, P/S, dividend yield/payout, EV/EBITDA) — each result interpreted in plain business terms with healthy/caution/concern or compare-to-peers; benchmarks research-verified (CFI/Investopedia/lender norms) — plus home affordability (28/36 DTI rule), retirement/FIRE (projection + 4% rule) and 50/30/20 budget — exact, private, educational (not advice); no live rates |
| Mathematics | 31 tools, exact arithmetic — fractions with steps, primes (Miller–Rabin), quadratics with radical roots, statistics, Roman numerals, nCr/nPr at BigInt scale, triangle solver (law of sines/cosines, ambiguous SSA), matrix calculator (det/inverse/multiply), logarithm (any base + antilog) |
| Biology & Lab | 16 tools — DNA reverse-complement/translate (sequence never uploaded), restriction-enzyme digest (26 enzymes, fragment sizes, linear/circular), protein pI & net charge (titration curve), C₁V₁=C₂V₂ dilution + serial planner, Punnett (mono/di/trihybrid), Hardy–Weinberg + χ², GC/Tm, DNA & protein molecular weight, molarity, hemocytometer, Michaelis–Menten, qPCR efficiency, doubling time |
| Chemistry & Lab | 40 tools — titration (unknown conc. from equivalence point), Raoult's law (vapour-pressure lowering), molality (mol/kg), mass percent (w/w), osmotic pressure (π=iMRT), interactive periodic table (all 118 elements, click for full details, colour by category/phase/block/electronegativity, full-screen), electron configuration, element comparison, oxidation-number solver, average atomic mass, molar mass / molecular weight (parses hydrates like CuSO₄·5H₂O + nested groups) with percent composition, chemical equation balancer (exact integer coefficients via BigInt null-space — correct on redox), stoichiometry (limiting reagent + theoretical yield), empirical/molecular formula, mole ↔ grams ↔ particles, molarity, dilution (C₁V₁=C₂V₂), percent yield, density, ideal / combined gas law, specific heat, pH, weak-acid/base pH (exact ICE quadratic from Ka/Kb), Ksp ↔ molar solubility (+ common-ion effect), equilibrium constant Kc (ICE solver + reaction quotient), Hess's law (ΔH°rxn from formation enthalpies), Henderson–Hasselbalch, Beer–Lambert, half-life, Gibbs free energy, Nernst, Arrhenius, freezing-point depression / boiling-point elevation, ppm, percent error |
| Statistics | 13 tools — normal distribution (z↔p, shaded bell curve via exact erf), binomial probability (BigInt-exact coefficients), confidence intervals (mean z/t + proportion), sample size, p-value (z/t/χ²/F, one/two-tailed), linear regression & correlation (least-squares + scatter plot, r, r²), t-test (one-sample/two-sample Welch or pooled/paired, exact p + significance verdict), Poisson distribution (P(X=k)/cumulative, mean=variance=λ), chi-square test (goodness-of-fit + independence, expected counts) |
| Physics | 41 tools — terminal velocity (√(2mg/ρACd)), magnetic force (Lorentz qvB / wire BIL), pressure (P=F/A), buoyancy (Archimedes, float/sink), escape velocity (√(2GM/r), Solar-System presets), latent heat (Q=mL), SUVAT kinematic-equations solver (enter any 3 of u/v/a/s/t), projectile motion with trajectory graph, free fall, Newton's 2nd law, momentum, 1D collisions (elastic/inelastic + restitution), friction, kinetic/potential energy, work, power, Hooke's law, centripetal force, Newton's gravitation, Coulomb's law, wave speed (v=fλ), standing-wave harmonics (string/open/closed pipe), Snell's law (critical angle + TIR), Ohm's-law V/I/R/P wheel, series/parallel resistors & capacitors, wave/SHM visualizer, Doppler effect, lens & mirror equation, torque, orbital velocity, Carnot efficiency, thermal expansion, photon energy (E=hf), de Broglie, special relativity (Lorentz γ, time dilation, length contraction), E=mc² |
| Size Converters | ring, shoe, bra, clothing, hat sizes across systems |
| Home & DIY | 24 tools — paver & patio (pavers + gravel base + bedding sand), trim & molding (baseboard/crown from perimeter − doors), retaining wall (blocks/courses/caps + base gravel), brick & block (count per wall + mortar joint + waste), excavation (volume, soil weight, swell, truckloads), rebar (bars each way, length, weight by ASTM size, tie-wire count), roof pitch (rise/run → x-in-12, degrees, slope %, rafter length), stair calculator (rise/run/stringer + IRC limits), wall stud calculator (16/24″ OC + plates), BTU / AC sizing (ENERGY STAR), — paint, tile & flooring, concrete (+ pre-mix bags), mulch & soil, wallpaper, gravel & aggregate (volume + tonnes), drywall/plasterboard (sheets), roofing (squares + shingle bundles via pitch), sod & grass seed, fence (posts/panels/rails), deck boards, board-foot lumber — metric or imperial |
| Electronics & Circuits | 15 tools — resistor color code (4/5/6-band, live visual resistor, IEC 60062), SMD resistor code (3/4-digit, EIA-96, R-notation, 0-ohm), LED resistor (series R + nearest E12 + power), voltage divider, capacitor code (104 → 100 nF), wire gauge (AWG diameter/area/resistance/ampacity), RC time constant & −3 dB cutoff, LC resonant frequency (tank + √(L/C)), 555 timer (astable/monostable), battery life — standard formulas + IEC/AWG/EIA data, Node-tested |
| Photography | 12 tools — depth of field (near/far limits by sensor+lens+aperture), field of view (angle + frame size), crop factor (equivalent focal length/aperture), exposure value (EV + equivalent exposures), hyperfocal distance, time-lapse planner, print size/DPI, Sunny 16 exposure — standard optics formulas, verified sensor data, Node-tested vs DOFMaster |
| Travel & Trips | 10 tools — flight distance (great-circle via haversine, distance/bearing/rough time on a live world map), flight time (distance ÷ cruise + overhead), layover & connection checker (vs typical minimum connection time), jet lag (days to adjust, east vs west), tip-by-country (customary rates for 14 countries + bill split), road-trip time (distance/speed/breaks → arrival), travel budget (per-day/per-person split), luggage size (litres + linear vs cabin/checked limits) — exact geometry, research-verified real-world data with caveats, Node-tested |
| 3D Printing | 8 tools — filament weight & length (cylinder geometry × density, 1kg PLA ≈ 335 m), filament cost (grams → price), print electricity cost (W × time × rate), model scale (linear vs cube-rule volume, + fit-to-bed), E-steps calibration (100 mm test), flow / extrusion multiplier (single-wall method), volumetric flow (mm³/s vs hotend limit), resin cost (mL + waste) — exact geometry + standard calibration formulas, cited densities (Simplify3D/Prusa/Formlabs), Node-tested |
| Solar & Energy | 10 tools — solar panel output (kWh/day/month/year from peak sun hours × derate), off-grid load (editable appliance table → daily Wh), battery bank sizing (Ah from load, autonomy, DoD, voltage), inverter size (running + surge), appliance energy cost (W × h × rate), solar payback (net cost ÷ savings), DC voltage drop (2·L·I·ρ/A vs NEC 3% / solar 2%), battery charge time (Ah/A + C-rate) — industry-standard formulas, values verified vs NREL/PVWatts + battery refs, Node-tested |
| Homebrewing | 12 tools — ABV ((OG−FG)×131.25 + Hall's accurate formula, attenuation, calories), IBU (Tinseth model, editable hop-additions table), priming sugar (CO₂ stoichiometry, bottle carbonation), Brix↔SG, hydrometer temperature correction, strike water (Palmer, metric/imperial), gravity dilution, refractometer FG (Sean Terrill cubic + WCF) — established brewing formulas verified vs Palmer/Tinseth/Terrill, Node-tested |
| Astronomy & Space | 13 tools — moon phase (synodic-month, phase/illumination/age), sunrise & sunset (NOAA solar algorithm, ±1 min), golden hour & blue hour (twilight windows by sun-elevation, reuses the NOAA solar algo), weight on other planets (NASA gravity ratios), age on other planets (orbital periods), light travel time (km↔AU↔ly↔parsec), angular size (small-angle), star magnitude & distance (distance modulus, Pogson brightness), telescope optics (magnification/f-ratio/Dawes/Rayleigh), stellar parallax (parsecs↔ly), redshift (z↔velocity, wavelength shift, Hubble distance, relativistic) — sourced constants, Node-tested vs NASA/NOAA |
| Weather & Atmosphere | 15 tools — density altitude (aviation, pressure alt + temp), snow load (roof, lb/ft²/kPa), absolute humidity (g/m³, Magnus), VPD (vapour pressure deficit, kPa, grow-stage zones), rainwater collection (roof harvest, L/gal), heat index (NWS Rothfusz, temp+humidity→feels-like + risk), wind chill (2001 NWS + frostbite times), dew point (Magnus/Alduchov–Eskridge), relative humidity (from temp+dew point), feels-like (heat index/wind chill by regime), wet-bulb (Stull 2011, 35°C survival limit), Beaufort scale (0–12), cloud base (dew-point-spread rule) — °C/°F, verified against NWS values, Node-tested |
| Music & Audio | 13 tools — note frequency (note↔Hz↔MIDI, equal temperament, adjustable A=432), chord & scale finder (build from a root or identify from notes, piano diagram), BPM→delay time (straight/dotted/triplet + Hz), tap tempo BPM counter, online metronome (sample-accurate Web Audio, accented downbeat), interval calculator (semitones/cents/ratio), chord transposer (+capo), audio file size (PCM), bar/time-signature duration — exact music maths, Node-tested |
| Gardening & Plants | 11 tools — growing degree days (GDD), pond volume & liner, spray/pesticide mix (oz-gal / mL-L), — plant spacing (square grid + triangular offset which fits ~15.5% more), seed & row spacing, raised-bed soil volume (L/ft³/yd³/bags), fertilizer nitrogen rate (from N-P-K + area), garden watering (~1 in/wk, 0.623 gal/ft²/in), planting dates from your last frost (16 crops), grow-light DLI (PPFD × hours), compost C:N ratio (greens + browns → 25–35:1) — metric/imperial, extension-sourced, Node-tested |
| Pets & Animals | 11 tools — dog age (dog↔human years via the 2020 epigenetic formula 16×ln(age)+31 + size-based chart — busts the ×7 myth), cat age (15/+9/+4 chart + life stage), dog & cat food portions (RER 70×kg^0.75 × MER life-stage factor → cups), pet gestation due dates (13 species), aquarium volume (L/US-gal/UK-gal), pet water intake (~50–60 ml/kg), dog crate size (AKC +2–4 in) — vet-sourced formulas, Node-tested |
| Fitness & Exercise | 10 tools — running pace (pace/time/distance, min/km + min/mile, race presets), pace converter (min/km ↔ min/mile ↔ km/h ↔ mph), one-rep max (Epley/Brzycki/Lombardi + %-of-1RM table), heart-rate zones (Tanaka/Karvonen/Gulati), race time predictor (Riegel), VO2 max (Cooper test), calories burned (ACSM MET, Compendium values), steps → distance — sourced formulas, Node-tested |
| Automotive | 15 tools — EV charging time (battery/SoC/charger kW), power-to-weight (hp/tonne, W/kg), stopping distance (reaction + v²/2μg, grip presets), tire size calculator (decode 225/45R17 → overall diameter, sidewall, circumference, revs/mile), tire comparison & speedometer error (true speed = indicated × new/old diameter), gear ratio & RPM (road speed ↔ engine RPM via gear × final drive × tire), engine displacement (π⁄4 × bore² × stroke × cylinders → L/cc/ci), compression ratio, horsepower ↔ torque (HP = T×RPM/5252 + kW/N·m), fuel economy (US↔UK MPG↔L/100km↔km/L, handles the different gallons), wheel offset ↔ backspacing — exact geometry, Node-tested |
| Cooking & Kitchen | 15 tools — brine calculator (salt % by weight), air-fryer conversion (−25°F, −20% time), roast cooking time (min/lb by cut + USDA temps), — grams ↔ cups (ingredient-aware: flour 120 g, sugar 198 g, honey 336 g per cup — King Arthur weights), cooking measurement converter (US/metric/imperial volume, exact NIST factors, flags US-vs-imperial gallon & 20 mL Australian tbsp), butter (sticks↔cups↔grams), oven temperature (°F↔°C↔gas mark + fan, snapped to the standard cooking table), recipe scaler (fractions), baking pan size (by area), baker's percentage / hydration, yeast (active dry↔instant↔fresh), coffee-to-water ratio, USDA meat temperatures — sourced, private |
| Text Tools | 26 tools — number to words (+ cheque "amount in words"), upside-down text generator, random line picker (raffle/winner, crypto-random), — "the invisible & exact layer of text": invisible-character detector (AI-watermark / zero-width), homoglyph/lookalike detector, text diff (LCS), readability (Flesch/FK/Fog/SMOG/CLI/ARI), Unicode inspector, word frequency, text cleaner (em-dash/smart-quote), Unicode normalizer, plus counters, case, sort, dedupe, find & replace |
| Charts & Design | 6 chart makers (10 self-hosted fonts embedded into exports, custom text/series/background colors, transparent bg) — bar, line, pie & donut, funnel (conversion stages + %), radar/spider (multi-axis profile), waterfall (running total, +/- floating bars) — paste “label, value” lines, pick a palette, download a crisp 2× PNG or an editable SVG; drawn with SVG in your browser, nothing uploaded |
| Fonts & Typography | 24 tools — fancy font & text generator (21 Unicode styles: 𝗯𝗼𝗹𝗱, 𝘪𝘵𝘢𝘭𝘪𝘤, 𝓼𝓬𝓻𝓲𝓹𝓽, 𝔣𝔯𝔞𝔨𝔱𝔲𝔯, 𝕕𝕠𝕦𝕓𝕝𝕖-𝕤𝕥𝕣𝕦𝕔𝕜, ᴍᴀʟʟ ᴄᴀᴘꜱ, ⓑⓤⓑⓑⓛⓔ, ｗｉｄｅ, s̶t̶r̶i̶k̶e̶ — real Unicode you can paste into Instagram/TikTok/X bios, gaps patched from Letterlike Symbols so no blank boxes), plus focused bold, italic, cursive, small-caps, bubble, wide, strikethrough, superscript/subscript & emoji-letter generators — a glitch/Zalgo (cursed text) generator with a madness slider, an invisible / blank name generator (Free Fire, WhatsApp, Discord), a symbols & special-characters copy-paste picker (arrows, stars, hearts, math…), a Discord colored-text (ANSI) generator, a text repeater, a mirror / backwards text generator, a Lenny face & kaomoji picker — and for CSS/design: px↔rem converter, modular type-scale generator (golden ratio + 7 more → copy-paste custom properties), line-height calculator (comfortable-reading bands), clamp() fluid-typography generator, gradient-text (background-clip) generator with PNG export, and a line-length / measure calculator (45–75 CPL), and an ASCII-art / big-text generator (self-contained FIGlet renderer, 10 classic fonts — Standard, Big, Slant, ANSI Shadow… — with kerning, copy & .txt download) — all client-side, nothing uploaded |
| Color Tools | HEX/RGB/HSL/CMYK, HSV/HSB converter, Delta-E (CIEDE2000 + CIE76 color difference), Kelvin→RGB (color temperature), OKLCH/OKLAB/LAB converter (CSS Color 4 + gamut-mapped HEX fallback), WCAG contrast + accessible-color fixer, APCA (WCAG 3) checker, contrast grid, color-blindness simulator (Machado 2009, image + palette), harmony generator, image color picker + palette extractor (median-cut, EyeDropper API), nearest color-name finder (CIEDE2000), Tailwind OKLCH scale generator, brand color finder (1,100+ palettes) |
| File & Data | CSV/JSON/XML/YAML, TOML↔JSON, XML formatter/minifier, Markdown↔HTML (HTML→Markdown via Turndown), Excel↔data (xlsx→CSV, xlsx→JSON, CSV→xlsx via SheetJS), e-invoicing viewers: Factur-X (FR), KSeF FA(3) (PL), Peppol BIS (BE), XRechnung/ZUGFeRD (DE) |
| Developer Tools | Base64, Base32 (RFC 4648), hashes, HMAC (SHA-1/256/384/512, keyed), JWT decoder + JWT encoder/signer (HS256/384/512), regex, number-base, query-string parser (↔ JSON), HTTP status code lookup, LLM token counter (exact o200k), IBAN validator (ISO 13616 mod-97), ISBN-10↔13 converter, Punycode/IDN converter (xn--), JSON diff (semantic, key-aware), Ethereum unit converter (BigInt-exact wei⇄ether), Keccak-256/SHA-3 + function selector, EIP-55 address checksum, JSON string escaper/unescaper, Unicode escape converter (\uXXXX ↔ text), text ↔ hex converter (UTF-8) |
| Network & IT | IPv4/IPv6 subnet calculators (exact 128-bit), CIDR, chmod, cron parser, MAC/EUI-64, download-time & bandwidth (Mbps↔MB/s) converters |
| Generators | 16 tools — QR code scanner/reader (decode a QR from an image via jsQR), dice roller & coin flip (crypto-random), MAC address generator, test credit-card numbers (Luhn-valid, clearly test-only), password, passphrase (EFF diceware), UUID v4/v7 · ULID · NanoID + decoder, QR, WiFi/vCard/email QR, barcode (EAN/UPC/Code128, check-digit), random number, lorem ipsum |
| Date & Time | timestamps, age, days-between, date add/subtract, week number, business/working-days, time-duration (hours between two times), DST-aware timezone pairs |
| Calendars | Hijri/Hebrew/Persian/Julian, Nepali BS⇄AD, 4-5-4 retail |
| Codes & Ciphers | Morse (with audio), NATO, binary, Caesar, Vigenère |
| Productivity | Pomodoro, Kanban, mind map, flowchart, swimlane diagram maker (cross-functional process flow — lanes per role, snap-to-grid steps, hand-off arrows), interactive Gantt (drag bars to reschedule/resize, zoom, full-screen), habit tracker — saved locally, JSON/PNG/PDF export |
| Privacy & Security | EXIF remover, AES-256 file encryption, file hash, TOTP/2FA code generator (RFC 6238, live countdown — secret never uploaded), bcrypt hash generator & verifier (tunable cost, salted), PII redactor (mask emails/phones/SSNs/cards[Luhn]/IPs/IBANs in text before pasting into AI — 100% client-side) |
| Image Tools | 18 tools — compress, convert, resize, resize to an exact KB target (passport/exam upload limits — binary-search JPEG/WebP quality + downscale), crop (rectangular + aspect presets), flip/mirror, favicon generator (one image → full PNG set + multi-size favicon.ico + manifest + HTML snippet, zipped), watermark (text, opacity, tiled diagonal), HEIC→JPG (libheif wasm), image→Base64, rotate (90/180/270 + EXIF-orientation fix), circle crop (transparent-PNG avatars), split image, EXIF metadata viewer, annotate, SVG→PNG (rasterise at any size), Base64→image (decode data URLs), combine images (stitch vertical/horizontal) |
| Photo Size Maker | passport / visa / ID photos for multiple countries — crop to exact official size, on-device face-position check (MediaPipe BlazeFace), background & exposure checks, DPI-correct export; every spec cited + date-verified |
| PDF Tools | 12 tools — merge/split/rotate with live page previews, JPG↔PDF (PDF→JPG/PNG rendered in-browser via pdf.js, + images→PDF), unlock/protect (qpdf wasm), accessibility checker (EAA), redaction checker + rasterizing redactor, text watermark (size/opacity/45° diagonal), page numbers (position, start-at, skip cover) |
| Audio & Video | 9 tools — trim, speed, volume, WAV convert (Web Audio), audio merger, video frame extractor (scrub + capture a still at native resolution via <video> + canvas — no ffmpeg.wasm, so no COOP/COEP headers and no 25 MB download), subtitles: SRT→VTT, VTT→SRT, subtitle shifter/resync (pure-JS cue parsing) |
Plus 121 in-depth guides on the blog — each with custom infographics, FAQ schema and cited sources — and a research-driven build pipeline (see docs/research/) that has shipped regulatory-deadline tools ahead of the French, Polish and Belgian e-invoicing mandates.
npm install
npm run dev # dev server at localhost:4321
npm run build # static site → dist/ (~1,050 pages)Two cooperating bots keep the live tools healthy, running entirely in GitHub Actions with no LLM / no
Claude tokens — see docs/AUDIT-SYSTEM.md for the full spec.
- Bot 1 — Auditor (
scripts/audit-ux.mjs) audits 10 rotating tools/day (plus any awaiting verification) on the live site with headless Chromium + axe-core, across functionality, input→output, SEO/metadata, content quality, accessibility, performance, mobile and privacy. It writes a git-tracked ledger (audits/ledger.json) and a dated report. - Bot 2 — Fixer (
scripts/audit-fix.mjs) applies safe, deterministic fixes to open findings — gated by a full build that reverts on failure — marks themverifying, and compiles everything that needs human/AI judgement intoaudits/recommendations.mdwith reasoning. - The loop: the next day's Auditor re-tests fixed tools →
completeif resolved, orchallenged(with reasoning) after 3 failed attempts.
Orchestrated by .github/workflows/audit.yml (daily 06:17 UTC + manual run). Everything is committed
under audits/ (public) — glance at audits/DASHBOARD.md for an always-current
view (scores, coverage, what was fixed, what's open/challenged). No email; the git files are the record.
Framework. Astro with 100% static output (output: 'static'), interactive
Preact islands hydrated per-tool, Tailwind CSS 4 and
TypeScript throughout. Pages are generated from typed registries under src/data/, so a
new tool is a data entry plus (where needed) one island. The build is plain static files — deployable
to any host, no SSR, no serverless, no backend.
The privacy model. There are no processing servers. Every computation — parsing, encoding,
cryptography, image and PDF manipulation, and machine-learning inference — happens on the user's
device. Anything heavy is loaded lazily on first use and self-hosted under
public/vendor/ so nothing is fetched from a third-party CDN. Tool content — the files
you open and the values you type — is never uploaded, and that promise is architectural, not a policy.
Site usage is measured with Google Analytics (GA4) — but only after a cookie-consent banner (Google
Consent Mode v2; analytics_storage denied by default, so no cookies/data until the visitor accepts). It records
page visits and engagement (see the privacy policy and cookie statement, with an opt-out); it only ever sees that a page was visited, never the content processed on it. The other network call
after page load is an optional star rating: a tiny PHP endpoint (api/rate.php) that
fires only when a user clicks to rate a tool and stores just the tool name, star value and a timestamp —
no IP address, no cookie, no user agent, no identifiers. (Standard host access logs apply, as with any site.)
On-device models & engines — what does the heavy lifting, and where:
| Engine / model | Used for | How it runs |
|---|---|---|
| MediaPipe BlazeFace (short-range) | Photo Size Maker — detects the face and derives head-height %, eye line, centering and tilt for the passport/visa compliance check | Google's face-detection model (blaze_face_short_range.tflite, ~230 KB) + the Tasks-Vision WASM runtime, self-hosted at /vendor/mediapipe/, lazy-loaded on first "Check photo". Falls back to the native Shape Detection API, then to manual guides |
| Canvas 2D API | Photo crop/resize/matte + export (with JFIF DPI patched into the file), image compress/convert/resize, PDF page rasterizing | Native browser image codecs — decode, resample, re-encode JPEG/PNG/WebP |
| libheif (WASM) | HEIC/HEIF → JPG/PNG decoding | ~1.2 MB WASM decoder, loaded only when converting |
| qpdf (WASM) | PDF unlock / password-protect | WASM build at /vendor/qpdf.wasm |
| pdf.js | PDF page previews, accessibility (tag-tree) checker, redaction text-layer extraction | Mozilla's PDF engine + its worker |
| gpt-tokenizer | LLM token counter — exact o200k_base/cl100k_base counts |
Pure-JS BPE tokenizer, runs in-browser |
| qrcode + JsBarcode | QR codes (URL/WiFi/vCard/email) and 1-D barcodes (EAN/UPC/Code128) with mod-10 check digits | Client-side canvas/SVG render, PNG/SVG export |
| Text-forensics + readability libs | Invisible-character & homoglyph detection, exact LCS text diff, Flesch/FK/Fog/SMOG/CLI/ARI readability | Pure TS (textscan, textdiff, readability), Node-tested |
| Web Crypto API | AES-256-GCM file encryption, SHA-2 file hashing, PBKDF2 key derivation, secure password generation | Native browser cryptography |
| Web Audio API | Audio trim / speed / volume / WAV conversion | Native, decodes to AudioBuffer |
Intl.DateTimeFormat (ICU) |
World-calendar conversions (Hijri, Hebrew, Persian, Coptic, Ethiopic, Buddhist, Julian…) | The browser's bundled ICU calendar data; reverse conversion by binary search over the day number |
| BigInt / rational arithmetic | Exact math (primes via Miller–Rabin + Pollard rho, fractions, nCr/nPr), IPv4/IPv6 (128-bit) subnetting | Plain TypeScript, no floating-point rounding |
Self-hosting the WASM/model assets means the strict "no third-party requests" promise holds even for the ML features — you can verify it in DevTools' network tab.
The full source is public so you can read, audit, and verify it — including the promise that everything runs in your browser and nothing is uploaded. It's source-available, not open source (LICENSE): small excerpts are fine for personal or educational projects, but redistributing it, hosting a copy, running a competing service, or reusing the written/blog content isn't — ask first for anything commercial. Notable building blocks worth reading:
- Conversion engine:
src/data/units/— self-contained, dependency-free TypeScript (exact factors, linear transforms). Copy the folder and callconvert(value, from, to). - Exact math:
src/lib/mathx.ts— rational arithmetic, Miller–Rabin, Pollard rho, Euclid with steps;src/lib/quadratic.ts— exact quadratic solver with simplified radicals. Node-tested. - Network math:
src/lib/net.ts— IPv4/IPv6 (BigInt) subnetting, CIDR sets, cron parsing, EUI-64. - E-invoice parsing:
src/lib/ksef.ts+ the EN 16931 UBL/CII parser insrc/components/file/EInvoiceTool.tsx. - Converter UI:
src/components/UnitConverter.tsx— a single Preact component you can drop into any Preact/React project. - Passport-photo engine:
src/components/photo/PhotoMaker.tsx(crop + guide overlay + DPI-correct export) with the compliance checks insrc/lib/photo-checks.tsand the self-hosted MediaPipe face detector insrc/lib/face-model.ts; country specs (each source-cited) live insrc/data/photo/.
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