Free online tools that keep your files on your computer
John's page of small, free utilities for PDFs, images, data and code. No ads, no sign-up and no upload limit — and nearly all of them do their work inside this tab, so the files you open never leave your machine. Why that matters.
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Elementary School Tools
Documents & textView all
PDF Toolkit
Client-side PDF merging, editing, annotation, and splitting — nothing leaves your browser.
EPUB Reader
Open an ebook from Gutenberg or your library and read it here, with a contents list and adjustable text size.
DOC Viewer
Open .doc and .docx files, make quick edits with a basic toolbar, then download as .doc or HTML — all in your browser.
HTML to Markdown
Paste a chunk of a web page and get clean Markdown back — headings, links, lists, code and tables.
Markdown Toolkit
Write Markdown with a live HTML preview, then copy or export to HTML or PDF.
OCR Toolkit
Pull the text out of an image or scanned PDF — the recognition runs in your browser, so the file is never uploaded.
Calendar Viewer
Open an .ics invitation or calendar export and actually read it — times, places, attendees and repeats.
Text Toolkit
Count words and characters, transform case, sort and dedupe lines, and generate placeholder text.
Images & visualsView all
Audio Trimmer
Cut a clip out of an audio file by dragging on the waveform, with optional fades — exports at full quality.
Image Toolkit
Resize, crop, compress, and convert images — and strip EXIF metadata — entirely in your browser.
Font Viewer
Drop a .ttf, .otf or .woff to see its metrics, embedded licence and every glyph it contains.
Color Toolkit
Pick colors, build harmonious palettes, convert HEX/RGB/HSL, and check WCAG contrast.
GPX Viewer
Map a GPX, KML or TCX track, see distance, ascent and duration, and export it as GeoJSON.
QR Code Toolkit
Generate QR codes for links, Wi-Fi, and contacts — with colors and a logo — and scan codes from images.
Barcode Generator
Make EAN, UPC, Code 128 and ten more barcode formats, and export them as sharp SVG or PNG for labels.
SVG Optimizer
Strip the metadata and rounding cruft out of an exported SVG, with a before-and-after preview.
Diagram Toolkit
Write a flowchart, sequence or ER diagram as text and watch it draw itself — then export SVG or PNG.
3D Model Viewer
Open an STL, OBJ, PLY or GLTF, orbit around it, check the triangle count, and save a picture.
Board Studio
A simple whiteboard for diagrams and planning — drop boxes, ellipses, and sticky notes, then connect them with arrows.
Data & formatsView all
Archive Toolkit
Build a ZIP from a pile of files, or open one and pull individual files out — without installing anything.
CSV Toolkit
Open a big CSV without Excel mangling it — check it, convert to JSON, and chart a column.
Format Converter
Convert between JSON, YAML and XML in either direction, with a live preview and a one-click swap.
JSON Toolkit
Format, minify, validate, and sort JSON — with key sorting and instant size feedback.
SQL Playground
Run real SQLite queries against a database file or a CSV — without uploading your data anywhere.
Unit & Base Converter
Convert length, mass, temperature, data, and more — plus binary, octal, decimal, and hex.
Code & developerView all
Code Formatter
Tidy JavaScript, TypeScript, CSS, HTML, JSON, YAML and Markdown with Prettier — without pasting code into someone else's server.
Cron Explainer
Turn a cron expression into plain English, break it into fields, and see the next five times it fires.
Diff Toolkit
Compare two blocks of text or JSON side by side, with highlighted additions and removals.
JWT Decoder
Read a token's header, claims and expiry — and check an HMAC signature — without it leaving the tab.
UUID & ID Generator
Generate UUID v4/v7, Nano IDs, and hex tokens in bulk — cryptographically random.