About Filum

What it is

Filum is a file conversion platform. It converts PDF, Word, Excel, PowerPoint, and other document formats with the highest fidelity available from open-source tools, provides a quality score for every conversion, and deletes the file within 60 minutes. No account is required for any conversion on the free tier.

The ten most common format pairs — PDF to Word, Word to PDF, PDF to Excel, Excel to PDF, and so on — are available without signing up, without entering an email address, and without a payment method. Ten conversions per day. Files up to 25 MB.

Why we built it

Document conversion is performed hundreds of millions of times per day. Every tool built to do it is anonymous. Users cannot name the service they used last week. They type a search, click the first result, convert the file, close the tab, and feel nothing. No trust. No memory. No preference.

The reason for that anonymity is not that the task is too mundane to matter. It is that every platform in the category has treated it as a commodity step — something to get through rather than something to get right. The result is a category full of tools that work adequately, treat user files carelessly, and communicate with users through dark patterns rather than honesty.

Filum is built on the premise that users who hand over a document containing their tax return, their employment contract, or their medical record deserve to know exactly what will happen to it, see that it was deleted, and trust that the platform has no interest in its contents. That premise is not complicated. Acting on it required building the entire architecture around it from the start.

How file handling works

Before any upload begins, Filum reads the first bytes of your file in the browser to confirm the file type matches what you selected, check whether the file is password-protected or corrupted, and extract metadata — page count, embedded fonts, creation date — so you can see what you are converting before pressing a button.

When you submit the file, it is uploaded to Supabase Storage with a 60-minute time-to-live set at the infrastructure level. The storage service enforces this TTL independently of the application. If the application fails, the infrastructure still deletes the file at 60 minutes. An application-level cleanup job runs every five minutes as a secondary confirmation. When you download the converted file and confirm receipt, the file is deleted immediately.

Every deletion is recorded in an append-only audit log. The log records the timestamp, file type, page count bracket, and deletion reason. It never records the filename, file content, or your IP address. The audit log table has a database-level row security policy that permits only INSERT — no UPDATE, no DELETE, by any role including the application itself. This means no one can alter or remove an audit record retroactively.

The conversion engine

Complex format pairs — PDF to Word, PDF to Excel, Word to PDF, and all Office format conversions — use Gotenberg with LibreOffice running on Railway infrastructure. LibreOffice is the most capable open-source document renderer available. Gotenberg exposes its capabilities through a predictable HTTP API.

Simpler operations — PDF text extraction, PDF merge for files under 25 MB, PDF split — run client-side using pdf-lib. These conversions happen in your browser, the file is never uploaded to a server, and the output is downloaded directly. Client-side conversion is noted where it applies.

What we do not do

• Email capture before a file downloads. The file downloads first. Always.
• Countdown timers on upgrade prompts. Fabricated urgency is a lie.
• Modals that interrupt a conversion in progress.
• Limits described without their actual number until after you hit them.
• Silent errors. Every failure states what happened and what to do next.
• Ads on the pricing page, developer portal, or status page.

Contact

For support, billing questions, privacy requests, and general feedback: hello@filum.se

We read every message. For conversion quality issues, attaching the source file and describing the expected output helps us understand the problem and improve the engine for the format pair in question.

Start converting

The free tier is functional without any setup. Ten conversions per day, 25 MB limit, no account required.