PDF Form Filler and Flattener

Fill and flatten PDF forms, privately

Fill in PDF form fields and flatten them into plain pages in your browser, with no upload. Your tax, rental or HR form never leaves this device.

Drop a PDF form here or choose a file

One PDF with fillable fields. Nothing is uploaded; everything happens on this device.

How it works

  1. Open your PDF form. Drop a fillable PDF on the page. The tool reads it on your device and lists every form field, grouped by page.
  2. Fill in the fields. Type text, tick checkboxes, pick radio options and dropdown values. Leave "Flatten after filling" on to lock the answers, or choose "Flatten only" to lock a form that is already filled.
  3. Save the PDF. Press Save PDF and you get yourfile_filled.pdf. Any field that could not be filled is listed so you can check it before sending.

Questions, answered

Are my files uploaded anywhere?

No. PDF Form Filler and Flattener runs entirely in your browser. Your form and everything you type into it are read into memory on your device, processed with JavaScript, and never sent to a server. You can disconnect from the internet and it keeps working.

What does flattening a PDF form do?

Flattening draws each field's value onto the page as normal content and removes the interactive field. The result looks the same but can no longer be edited in a PDF reader, which is what many offices ask for when they reject forms that can be changed.

Why does it say my PDF has no form fields?

The tool fills interactive (AcroForm) fields only. Scanned forms and PDFs with printed blank lines have no fields to fill, and XFA forms made with some older designer apps are not supported. It does not add free text or signatures to a page.

Some characters were reported as unsupported. Why?

Values are drawn with the standard Helvetica font built into every PDF reader, which covers Western European letters. Characters outside that range, such as emoji or non-Latin scripts, are flagged per field and you can replace them with the closest plain letters before saving.

Is it really free? Does it work offline?

Yes and yes. It is open source under the MIT license, with no account, no limits and no ads. After your first visit the page is cached by a service worker, so it loads without a connection, and you can install it from your browser's menu as an app.

Was this written by AI?

Yes. PDF Form Filler and Flattener was generated by Claude Code from a written specification inside an automated pipeline, with a test suite that runs in a real browser. The full source is on GitHub, so you can read every line before you trust it with your files.

Built by one person, given away for free

PDF Form Filler and Flattener is a free alternative to paid tools like Smallpdf and Sejda Flatten PDF. If it earns a place in your bookmarks, a coffee keeps the updates coming.

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