Image Optimization
Understanding Client-Side WebP Image Compression Algorithms
How VP8 intra-frame prediction and entropy coding shave 25–35% off image weight — and why the entire pipeline runs inside your browser tab on img.gotool.app.
Read Guidegotool.app · Ten privacy-first web apps
Ten focused web apps. One privacy protocol.
From Scripture study and QR codes to loan schedules, VAT, invoices and media compression — free, open-source utilities engineered to run entirely inside your browser.
No sign-up · No uploads · No tracking
Knowledge base
Field guides for practitioners
Long-form, no-fluff explainers on the algorithms, standards and arithmetic behind every app in the directory — the compression science, the tax formulas, the tokenization rules. Written to be read — not skimmed.
Audio Engineering
Audio Compression Explained: Codecs, Bitrate & Psychoacoustics
Why a 40 MB WAV becomes a 4 MB MP3 that sounds nearly identical. Perceptual coding, masking, and choosing a bitrate you won't regret — the engine behind audiocompress.gotool.app.
Read GuideQR Codes
How QR Code Error Correction Keeps Damaged Codes Scannable
Reed–Solomon parity lets a QR symbol survive up to 30% damage and still scan instantly. The four ECC levels — and when each one earns its keep in qr.gotool.app.
Read GuideUnit Conversion
The Mathematics of Unit Conversion: Precision, Rounding & Standards
A $125-million Mars spacecraft was lost to a unit mix-up. From SI base units to IEEE 754 rounding artefacts — what correct conversion takes, and how unitconvert.gotool.app gets it right.
Read GuideText & Search
Word Counting & Full-Text Search: From Essays to Scripture
What exactly is a “word”? Tokenization, Unicode edge cases and reading-time maths for wordcount.gotool.app — plus the inverted indexes that power instant search in bible.gotool.app.
Read GuideBusiness Finance
Profit, Margin & Markup: The Arithmetic of Getting Paid
Margin versus markup — the confusion that quietly wrecks pricing. The exact formulas, the mental shortcuts and the traps, as computed in profitcalc.gotool.app.
Read GuideLending Maths
Loan Amortization Explained: Interest, EMIs & Payoff Schedules
Compound interest, the annuity formula and the table that shows where every payment goes. Read a schedule like a lender — with loancalc.gotool.app.
Read GuideTax & Invoicing
VAT & Invoices Demystified: Tax-Inclusive Maths Done Right
Add or strip VAT without rounding drift, keep invoice totals internally consistent, and number documents like an accountant. Behind vat.gotool.app and invoicegen.gotool.app.
Read GuidePrivacy Engineering
Why Client-Side Processing Is the Future of Privacy-First Software
The safest database is the one that never receives your data. The engineering case behind all ten Gotool apps — and the honest limits of the approach.
Read GuideTool ecosystem directory
Ten focused subdomains, one shared engine
Each Gotool app ships as its own lightweight subdomain with a single job done exceptionally well. They share one design system, one privacy protocol and one promise: your files stay on your machine.
- bible.gotool.app Bible
- qr.gotool.app QR Codes
- wordcount.gotool.app Word Count
- profitcalc.gotool.app Profit Calc
- unitconvert.gotool.app Unit Convert
- img.gotool.app Images
- invoicegen.gotool.app Invoices
- loancalc.gotool.app Loan Calc
- vat.gotool.app VAT
- audiocompress.gotool.app Audio
Every app opens on its own subdomain under the same zero-upload guarantee. Prefer the long version? Read the full tool directory.
Core privacy protocol
Your data never leaves the browser tab
Every Gotool app is compiled to run exclusively inside your browser engine using client-side JavaScript and WebAssembly. Files are read into memory, transformed locally, and handed straight back to you.
- Zero server retention — there is simply nothing stored, because nothing is sent.
- No accounts, no sessions, no telemetry attached to your work.
- Once loaded, the apps keep working offline; the network is optional.
- Open-source code you can audit before you trust it.
The full contract is in our Privacy Policy and Cookie Policy.
About Gotool
Small tools. Serious engineering.
Gotool exists because most “free” web utilities quietly ship your data to a server: your screenshots, your contracts, your sermon notes, your invoices. We invert that model. The software travels to your data — never the other way round.
Every app in the directory — Scripture search, QR generation, word counting, profit and loan maths, unit conversion, image and audio compression, invoicing and VAT — shares that single rule: computation happens on your machine. Alongside each tool we publish the theory behind it, so you understand exactly what happens to your files and why the results are trustworthy. No dark patterns, no sign-up walls, no surprises.
10Live web apps
9In-depth field guides
0Bytes stored on servers