Any format. Any size. No wait.
Test File Generator for Any Format and Exact Size
Set the size, pick a format, and the file appears. It is assembled on your machine, so nothing is uploaded and nothing is downloaded from a server.
Popular tools.
Jump straight to the tools people reach for first.
Free file tools.
ByteRivet is also a full toolkit for files you already have — merge, convert and edit PDFs and images, free and without installing anything.
The file never travels.
Other generators keep a folder of pre-made files and hand you a link. That means fixed sizes and a wait proportional to your connection. Here the bytes are written where you already are.
- Runs locally
- No upload
- No account
- Works offline
Pick a family.
Every format has its own page with common sizes, structural notes and what the padding contains.
Archives
Packages and raw bytes for throughput tests. Download BIN and ZIP files at an exact size — no upload, no signup.
- BIN
- ZIP
Data
Tables and payloads for import limits and API body caps. Download CSV, JSON, SQL, XLSX and XML files at an exact size — no upload, no signup.
- CSV
- JSON
- SQL
- XLSX
- XML
Documents
Paper-shaped files for upload forms and print pipelines. Download DOCX, HTML, MD, PDF and TXT files at an exact size — no upload, no signup.
- DOCX
- HTML
- MD
- TXT
Images
Raster and vector, sized for avatar and gallery limits. Download JPG, PNG, SVG and WebP files at an exact size — no upload, no signup.
- JPG
- PNG
- SVG
- WebP
Media
Audio and video containers for ingestion queues. Download MP3, MP4 and WAV files at an exact size — no upload, no signup.
- MP3
- MP4
- WAV
System
Executables, scripts and disc images for platform and upload testing. Download BAT, EXE and ISO files at an exact size — no upload, no signup.
- BAT
- EXE
- ISO
Where the bytes go.
Padding is never appended junk. Each format has a region its own specification reserves for extra data, and that is the only place it is written.
| Format | Padding region | Opens in | Minimum |
|---|---|---|---|
| BIN | The entire file is pseudo-random printable bytes | hex editors like HxD or xxd, and Python's open() in binary mode | 1 B |
| ZIP | A payload file stored inside the archive without compression | Explorer, Finder, 7-Zip and unzip | 368 B |
| CSV | Additional rows, with the final row padded to land on the exact byte | Excel, Sheets, pandas and Python's csv module | 80 B |
| JSON | A trailing string field, so the document still parses | jq, browser devtools, Python's json module and Node's JSON.parse | 60 B |
| An unreferenced content stream, the same mechanism PDF writers use for incremental updates | Acrobat, Preview, Chrome, pdf.js and pypdf | 772 B | |
| DOCX | A binary part declared in [Content_Types].xml, which Word ignores | Microsoft Word, LibreOffice, Google Docs and python-docx | 1,496 B |
Questions.
What is ByteRivet?
A browser-based toolkit for files: an exact-size test file generator, plus PDF tools, image tools and format converters. Every tool is free, works without an account, and most of them never send your file anywhere.
Which tools run entirely in my browser?
The test file generator, all PDF tools (merge, split, organize, watermark) and all image tools (compress, convert, crop, resize, rotate) run locally using Web Workers. Nothing is uploaded, and they keep working with your network switched off.
Which operations need a server?
Only Office-to-PDF and PDF-to-Office conversion — they need a real document engine that can't run in a browser tab. The file is sent over HTTPS, converted, and deleted immediately afterward; the result is deleted after 15 minutes or as soon as you download it, whichever comes first.
Is ByteRivet free?
Yes — every tool, no account, no subscription, no watermarked or limited output.
Which formats are supported?
The test file generator covers 19 formats (PDF, PNG, JPG, WebP, ZIP, DOCX, XLSX, CSV, JSON, XML, HTML, SQL, MD, SVG, WAV, MP3, MP4, BIN and more). The tools handle PDF, common image formats, and Office documents — see the Formats and Tools menus for the full, current list.
Does ByteRivet work on mobile?
Yes, every tool is responsive and works in a mobile browser. Browser-based tools are limited by your device's available memory, so very large files can be slower on a phone than a desktop.
Does 1 MB mean 1,000,000 bytes?
It depends who you ask. 1,000,000 bytes is the decimal MB; 1,048,576 bytes is technically 1 MiB, though it is commonly still called "1 MB". ByteRivet currently uses the binary (MiB) convention. Some upload validators use decimal units, others use binary — the readout always shows the exact byte count, so there is never any ambiguity about what you are getting.
Can I use the generated files in an automated test suite?
Yes. Generate once and commit the file as a fixture, or run the same generators in Node for a reproducible pipeline.
Blog
Everything we measure, we write down.
We publish plain, technical, and practical content about file formats, upload limits, and conversion technologies.
View all posts →
File Upload Limits by Platform: The Complete 2026 Reference
Every major platform's file upload limit in one table — Gmail, Slack, Discord, WhatsApp, GitHub, and more — with a link to generate a test file at the exact size.
Test EXE Files: What They're For and How to Generate One Safely
A test .exe file with a real, valid header and zero executable code — useful for upload validation, security scanning, and installer-flow testing without any actual risk.
How to Test File Upload Limits: A Practical Guide
Testing an upload limit properly means three exact files, not one: at the limit, one byte over, and comfortably under — here's how and why.
How to Create a Test File of Any Size
Learn how to create exact-size test files for upload limits, API testing, email attachments, storage checks and QA workflows.