Safe Dummy File Generator with No Upload
You need a file to test a form. Not a real tax document. Not a customer export. Not the photo your phone helpfully named IMG_9384.HEIC. Just a harmless file that proves the upload button works.
That is exactly what a dummy file generator is for. It creates a file locally in your browser, gives it a custom file size, and downloads it. TrueFileSize does not receive the file content because there is no upload step.
Quick answer
Use the file generator when you need a harmless test file and do not want to upload anything private. It can create TXT, CSV, JSON, XML, HTML, LOG, BIN, SVG, Markdown, YAML, and TOML files up to 10MB.
For larger files, use Download Tests. For real document/media formats like PDF, DOCX, XLSX, MP4, or ZIP, use the existing prebuilt sample file collections.
What "no upload" actually means
The generator runs in your browser using standard Web APIs. It creates bytes in memory, wraps them in a Blob, and asks the browser to download that Blob as a file.
There is no request body containing your generated file. There is no storage bucket write. There is no backend job waiting to clean it up.
You can still download the generated file and upload it somewhere else if you choose to. That part is under your control.
When normal users need dummy files
This is not only for developers. Normal users run into file limits all the time:
- A job portal asks for a resume under 5MB.
- A contact form says "PDF only" but the error message is vague.
- A support portal accepts screenshots but rejects unknown formats.
- A website says it supports CSV import and you want to test the button first.
- A cloud folder workflow needs a placeholder file with a specific size.
Using a private dummy file is safer than uploading something personal just to test a form.
Why custom file size helps
The phrase "max 10MB" looks simple until you test it. Does the form reject exactly 10MB? Does it reject 10.1MB? Does it show the right message when the file is too large?
A custom file size lets you create small boundary tests without hunting through your downloads folder. Try:
| Need | File to generate | |---|---| | Quick upload smoke test | 1KB TXT | | CSV import preview | 100KB CSV | | Form limit near 1MB | 999KB and 1MB files | | Progress UI check | 5MB BIN | | Max generator limit | 10MB BIN |
If you need 100MB, 1GB, or 10GB, switch to the CDN-hosted large test files.
What formats are safe to generate locally?
Plain text and structured text are easy: TXT, LOG, Markdown, CSV, JSON, XML, YAML, TOML, and HTML. SVG is also text-based when the template is controlled. BIN is just raw bytes.
Complex formats are different. A "fake" PDF that is just text with a .pdf extension is not a PDF. A valid XLSX is a zipped package with XML parts. A real MP4 needs a media container. Generating those in the browser usually means adding heavy libraries and still risking invalid files.
That is why the generator intentionally stays small.
Use it safely
Open the file generator, pick a format, choose a preset or custom file size, download the file, and use it wherever you need a harmless placeholder. If the app you are testing cares about MIME types, check the expected value in the MIME Type Lookup.