Home › Developer Tools › Dummy File Generator
Dummy File Generator
Make a file of exactly the size you need to test upload limits, progress bars, quotas or transfer speeds. Pick zeros, incompressible random bytes or readable text, choose the extension and download it. Nothing is uploaded; the file is built in your browser.
Last updated:
Unit system
0%
File—
Exact size—
Also equals—
Generated in—
SHA-256—
Advertisement
Advertisement
How to use the Dummy File Generator
- Enter the size or click a preset such as 10 MB or 1 GB.
- Choose binary or decimal units to match the limit you are testing (most upload limits use binary megabytes).
- Pick the content: zeros for a quick file, random bytes to defeat compression, or text for a readable file.
- Set the extension and name, e.g.
.pdfto test a PDF-only upload field. - Press Generate & Download. The exact byte count and SHA-256 appear below when it is done.
Common test file sizes in bytes
| Size | Binary bytes (KiB/MiB/GiB) | Decimal bytes (KB/MB/GB) | Typical use |
|---|---|---|---|
| 100 KB | 102,400 | 100,000 | Avatar and form attachment limits |
| 1 MB | 1,048,576 | 1,000,000 | Default upload limits (e.g. nginx client_max_body_size is 1 MiB) |
| 2 MB | 2,097,152 | 2,000,000 | PHP's default upload_max_filesize |
| 10 MB | 10,485,760 | 10,000,000 | Document and image upload fields |
| 25 MB | 26,214,400 | 25,000,000 | Common email attachment limit |
| 100 MB | 104,857,600 | 100,000,000 | Video uploads, speed tests |
| 1 GB | 1,073,741,824 | 1,000,000,000 | Large-file and resumable upload tests |
What to test with a dummy file
- Size limits on both sides. Try exactly the limit, one byte over and one byte under. Client-side checks, the web server, the proxy and the application often have different limits.
- Error messages. Does a too-large file give a friendly message, or a blank page, a 413 Request Entity Too Large or a timeout?
- Progress and resume. Use 100 MB or more of random data to watch progress bars, pause and resume, and chunked uploads.
- Compression. A file of zeros may upload almost instantly through a compressing proxy, while random data shows the real throughput.
- Integrity. Compare the SHA-256 after a round trip to catch truncated or corrupted transfers.
Command-line equivalents
- Windows:
fsutil file createnew test.bin 10485760(zeros) - macOS:
mkfile 10m test.binorhead -c 10485760 /dev/urandom > test.bin - Linux:
truncate -s 10M test.bin(sparse) ordd if=/dev/urandom of=test.bin bs=1M count=10
Frequently asked questions
How many bytes is 10 MB?
It depends on the convention. In binary units (used by Windows, PHP's upload_max_filesize and many servers) 10 MB is 10 × 1,048,576 = 10,485,760 bytes, properly called 10 MiB. In decimal units (used by macOS, disk makers and network speeds) 10 MB is 10,000,000 bytes. Choose the unit system that matches the limit you are testing.
Which content type should I choose?
Zeros are fastest and fine for testing size limits. Random bytes cannot be compressed, so use them when testing transfer speeds, CDN or proxy behaviour or anything that may gzip the upload. Text and numbered lines create readable files for log viewers, editors and line-count tests.
Is a dummy .pdf or .jpg file a real PDF or image?
No. Only the file name ends in .pdf or .jpg; the content is zeros, random bytes or text. Upload forms that only check the extension or MIME type will accept it, but anything that opens or validates the file will report it as damaged. To test a real file, use a genuine document of the right size.
How do I test a file that is just over an upload limit?
Use the bytes unit. For a 10 MiB limit, generate 10,485,760 bytes to test the exact limit and 10,485,761 bytes to test one byte over. The Exact size card confirms the byte count of the generated file.
Why use the SHA-256 checksum?
After uploading and downloading the file again, compute its SHA-256 (for example with sha256sum on Linux, shasum -a 256 on macOS or Get-FileHash in PowerShell) and compare it with the value shown here. If they match, the file arrived unchanged. With random content even a single flipped byte changes the hash.
What is the largest file I can create?
Up to 2 GB. The file is assembled in browser memory before it is saved, so very large files need free RAM; on phones and tablets keep it to a few hundred MB. On a desktop you can also use fsutil file createnew (Windows), mkfile (macOS) or truncate / dd (Linux) for larger files.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.
Related tools
Random String GeneratorGenerate secure random strings and tokens in bulk with any length and character set.Hash GeneratorGenerate MD5, SHA-1, SHA-256 and SHA-512 hashes of text or files.Lorem Ipsum GeneratorGenerate placeholder text as paragraphs, words or lists, with HTML.Data Storage ConverterConvert bits, bytes, KB, MB, GB, TB and KiB, MiB, GiB, TiB with decimal and binary side by side.QR Code GeneratorMake QR codes for links, Wi-Fi, email and more.Barcode GeneratorCreate Code 128, EAN-13, UPC-A, EAN-8, Code 39 and ITF-14 barcodes as PNG or SVG.UUID GeneratorGenerate UUID v4 and v7 / GUIDs in bulk and copy or download them.Schema Markup Generator (JSON-LD)Create JSON-LD structured data for FAQ, Product, Article and more.Htaccess & Nginx Redirect GeneratorBuild 301 redirects for .htaccess, Nginx and Netlify or Cloudflare _redirects.Fake Data GeneratorGenerate mock data as JSON, CSV or SQL.API Key GeneratorCreate secure API keys and secrets with prefixes, checksums and SHA-256 hashes for storage.MIME Type LookupFind the MIME type for any file extension, or the extensions for a MIME type, in 400+ entries.Cron Expression GeneratorBuild crontab schedules visually, read them in plain English and see the next run times.URL Slug GeneratorTurn titles into clean, SEO-friendly URL slugs: accents, stop words, separators and bulk lines.JSON Schema GeneratorTurn sample JSON into a draft 2020-12 JSON Schema with types, required fields and formats.Gitignore GeneratorBuild a .gitignore from 50+ templates for languages, frameworks, IDEs and OS, merged and deduped.License GeneratorCreate a LICENSE file for MIT, Apache, GPL, BSD, ISC, MPL or Unlicense with your name and year.ULID GeneratorGenerate sortable ULIDs and UUID v7 in bulk, monotonic option, and decode their timestamps.Htpasswd GeneratorCreate .htpasswd entries with bcrypt, APR1-MD5 or SHA-1 for Apache and Nginx basic auth.Placeholder Image GeneratorCreate placeholder images in any size, color and text as PNG, JPG, WebP, SVG or data URI.Ads.txt GeneratorCreate or validate ads.txt and app-ads.txt files: seller lines, cert IDs and variables.Docker Run to Compose ConverterConvert docker run commands to docker-compose.yml, or a compose file back to docker run.Dockerfile GeneratorGenerate a production Dockerfile and .dockerignore for Node, Python, Go or a static nginx site.HTML Boilerplate GeneratorTick the options you need and get a clean HTML5 starter template with meta, OG tags and CSS reset.JSON to Zod SchemaInfer a Zod (or Yup) schema from sample JSON with optional, nullable and z.infer types.Linux Commands Cheat SheetSearchable Linux and bash command reference with flags explained, examples and copy buttons.LLMs.txt GeneratorBuild an llms.txt file for AI crawlers: summary and link sections, import from your sitemap.Nano ID GeneratorGenerate secure Nano IDs with custom alphabet, length and count, plus a collision calculator.Nginx Config GeneratorBuild an nginx server block: static site, SPA, reverse proxy or PHP, with SSL, gzip and redirects.OpenAPI / Swagger ViewerView OpenAPI 2/3 JSON or YAML as interactive API docs with validation and an endpoint list.package.json GeneratorFill a form and get a valid, npm-ready package.json with scripts, dependencies and checks.PKCE Code Challenge GeneratorGenerate an OAuth 2.0 PKCE code_verifier and S256 code_challenge, build auth URLs, verify pairs.README GeneratorFill in a form and get a polished README.md with badges, install, usage and license, live preview.Regex GeneratorBuild regular expressions visually from blocks or presets (email, date, phone) and test them live.Commit Message GeneratorBuild Conventional Commit messages with type, scope, body, breaking change and issue refs.Database Schema DesignerDesign tables and relationships visually, then export SQL for MySQL, PostgreSQL or SQLite.Docker Compose GeneratorBuild a docker-compose.yml with a form: services, ports, volumes, env, healthchecks and presets.FFmpeg Command GeneratorPick a task and options, get the exact ffmpeg command with every flag explained.Product Schema GeneratorBuild Product JSON-LD with price, availability, brand, GTIN, ratings and reviews.Question Keyword GeneratorFind the questions people ask about a topic, grouped by who, what, why, how, can and more.Recipe Schema GeneratorCreate Recipe JSON-LD with ingredients, steps, prep and cook times, nutrition and ratings.Security Headers GeneratorPick HSTS, CSP, frame, referrer and permissions options and get Apache, Nginx, Netlify or Cloudflare config.SKU GeneratorBuild consistent SKUs from brand, category, size and color, then export every variant as CSV.Typography Scale GeneratorBuild a modular type scale from a base size and ratio, then copy CSS variables or a Tailwind config.WordPress Salt GeneratorGenerate fresh WordPress security keys and salts for wp-config.php, .env or Docker in one click.ANSI Color Code GeneratorStyle terminal text with 16, 256 or RGB colors and get escape codes for bash, Python, JS and C.Apache Virtual Host GeneratorCreate an Apache VirtualHost config with SSL, redirects, reverse proxy or PHP-FPM in seconds.Bash Prompt GeneratorDrag and drop a custom PS1 prompt for bash or zsh with colors, git branch and a live preview.Changelog GeneratorTurn Conventional Commit messages into a grouped Keep a Changelog Markdown file per version.cURL Command BuilderBuild curl commands from a form: method, headers, query, JSON or form body, auth and flags.Docker Compose to KubernetesConvert docker-compose.yml into Kubernetes Deployment, Service, ConfigMap and PVC manifests.Docker Compose ValidatorCheck a docker-compose.yml for YAML errors, schema mistakes, broken references and deprecated keys.Dockerfile LinterLint a Dockerfile for best practices: pinned tags, apt cleanup, non-root USER and layer count.Dockerignore GeneratorBuild a .dockerignore from Node, Python, Go and Java templates, plus your own entries.ESLint Config GeneratorGenerate a flat eslint.config.js for JavaScript, TypeScript, React or Node with rule presets.Git Branch Name GeneratorTurn a ticket ID and title into a clean, valid git branch name like feature/PROJ-12-add-login.GitLab CI Config GeneratorGenerate a .gitlab-ci.yml with stages, jobs, images, cache, artifacts and rules from templates.Jinja2 Template TesterRender Jinja2 templates with YAML or JSON variables using real Jinja2, with clear error lines.JSON Schema Mock Data GeneratorGenerate realistic sample JSON from a JSON Schema: formats, patterns, $ref, seeds and counts.Kubernetes Secret GeneratorCreate Kubernetes Secret YAML from key/value pairs or .env with auto base64, or decode one.Kubernetes YAML ValidatorValidate Kubernetes manifests against the API schema of a chosen version, with error paths.Prettier Config GeneratorToggle Prettier options, preview formatted code live and copy your .prettierrc file.Quartz Cron GeneratorBuild and explain Quartz and Spring cron expressions with seconds, ?, L, W and #, plus next fire times.README Badge GeneratorCreate Shields.io-style README badges for license, version, build and custom labels.Systemd Service File GeneratorCreate a systemd .service unit with ExecStart, user, restart policy, environment and hardening.tsconfig.json GeneratorBuild a tsconfig.json with target, module, strict checks and path aliases, each option explained.Access Log AnalyzerAnalyze Apache and Nginx access logs: top URLs, IPs, status codes, bots and traffic charts.Regex String GeneratorGenerate random test strings that match any regular expression, checked against the real regex.