FillFox processes all PDF files entirely in your browser using JavaScript. Files are never uploaded to any server — the app has no backend that can access, read, or store your documents. Once you close the tab, your PDF data is gone from memory.

FillFox supports both interactive PDFs and non-interactive ("flat") PDFs. For interactive forms, it handles 4 field types: text boxes, checkboxes, radio buttons, and dropdowns. For flat PDFs — like scanned documents or locked forms — you can click anywhere on the page to place text. This covers tax forms, rental agreements, government paperwork, and most other documents.

FillFox offers two ways to sign a PDF. You can draw a signature using your mouse, finger, or stylus on a canvas, or type your name and have it rendered in a handwriting-style font. Both options produce a PNG image that gets embedded directly into the PDF on export. Pro users can also save signatures to a vault for reuse across multiple documents.

FillFox is free for all core features: filling form fields (text boxes, checkboxes, radio buttons, dropdowns), adding text overlays to flat PDFs, and drawing or typing signatures. Free use supports PDF files up to 100 MB with no daily limit. Pro costs $3/month and adds a signature vault for saving and reusing signatures, removes the file size cap, and removes ads.

FillFox works on phones and tablets in any modern mobile browser. You can fill form fields, draw signatures with touch input, type text onto non-fillable PDFs, and download the completed file — all without installing an app. The interface adapts to smaller screens with touch-friendly controls.

FillFox produces electronic signatures that are suitable for most everyday documents — rental agreements, tax forms, school enrollment, HR paperwork, and basic contracts. These qualify as electronic signatures under laws like the US ESIGN Act and EU eIDAS regulation for standard transactions. Some legal contexts (court filings, notarized documents) may require certified digital signatures with PKI verification, which FillFox does not provide.

After cancellation, Pro access continues until the end of your current billing period. Once it expires, you return to the free tier with the 100 MB file size limit. Signatures already saved in your browser remain accessible. You can re-subscribe at any time to regain Pro features.

Email [email protected] with your order number and a description of the issue.