Should you build your own FileChanger?
One API call converts documents, images, audio and video between a few hundred formats
The conversion is other people's software. Pandoc, ImageMagick and FFmpeg do the actual work, the format list looks enormous because those three projects are enormous, and a coding agent can wire all of them behind an upload form and a REST endpoint in one sitting. What a subscription buys is not the conversion, it is somebody else running a box that eats untrusted files from strangers all day without falling over, and keeping a few hundred format pairs working after every upstream release. Point it at your own files on your own machine and most of that risk simply is not yours, which is why this one is a yes.
ENOriginal research content in English. Original prompt preserved in English.
Build me a personal file conversion service in an empty repo. Requirements:
- Python 3.12, FastAPI, uv for dependencies, SQLite for job state. One process,
no broker, no microservices, no alternative stacks.
- Never write a converter. Shell out to pandoc for markup and documents,
LibreOffice headless for Office, ImageMagick for images, FFmpeg for media.
- POST /convert takes a file, a source and a target format and returns the bytes
below a size threshold set in config. Above it the same route returns a job
id, GET /jobs/{id} reports its state and GET /jobs/{id}/result streams the
file. One background worker thread is enough, do not add Celery.
- Build the format matrix at startup from `pandoc --list-input-formats`,
`--list-output-formats`, `ffmpeg -formats` and `magick -list format` rather
than hardcoding it, and serve it at GET /formats.
- Treat every upload as hostile: convert in a temp dir with a wall-clock
timeout, an output size cap and no network, then delete the inputs whether it
worked or not. Log the failing command and its stderr, never return either.
- Ship an MCP server over stdio using the official Python SDK, exposing convert
and formats as tools so agents can convert without going through HTTP.
- Authenticate with API keys stored hashed in SQLite. Show the plaintext once at
creation and support revocation.
- One HTML page, no JS framework: pick a file, pick a target from /formats,
download the result.
- One Dockerfile installing pandoc, typst, libreoffice-core, imagemagick and
ffmpeg, a compose file with a volume for the database, config in .env and a
committed .env.example.
- Out of scope: accounts, billing, metering, quotas, telemetry, multi-tenancy
and any hosted control plane.
- Test one round trip per engine (Markdown to PDF, PNG to WebP, WAV to MP3), an
oversized upload and a conversion that hits the timeout. README covers setup,
formats, security assumptions and where data lives. Finish by running the
tests and listing the commands used.The prompt opens pre-filled in your agent. Review it before running.
What would building your own look like?
Accept a file, shell out to pandoc, ImageMagick or FFmpeg depending on what it is, and hand the converted bytes back over HTTP or MCP.
What you will need
- pandoc
- FFmpeg
- ImageMagick
- LibreOffice headless for Office formats
- Typst or a LaTeX install if you want PDF out
Nobody pays for the conversions that work. They pay for the awkward ones: the DOCX with tracked changes, the HEIC nobody can open, the MXF from a camera, the 4 GB video that has to finish while a browser tab is still open. Doing those reliably means keeping a toolchain installed, patched and fenced off from the files it is fed, and doing it for other people means doing it while strangers upload whatever they like. That upkeep is the product. The convert button is a weekend.
xsandboxing, because your version runs files straight through the same toolchain as everything else on the machine
xthe long tail of format pairs, where the fix is usually a missing font, a filter flag or an upstream bug
xqueueing and timeouts for large video, which is where the compute bill actually lives
xa hosted MCP server and API keys your other tools can reach from anywhere, not just from localhost
xsomebody else being on call when a LibreOffice or LaTeX upgrade quietly breaks PDF output
Prefer something ready-made?
PandocIf the job is only documents, the paid service is a web form on top of this. Installer, twenty years of releases, and no upload step.Open source↗
ConvertXA self-hosted web converter that wraps the same engines, with accounts and a job list already built. One container and you own the whole pipeline.Open source↗
VERTConverts images and documents in the browser tab itself, so the file never leaves the machine. Video is the exception and needs their server or yours.Open source↗View all 3 alternatives to FileChanger →· Licença, instalação e limitações em cada alternativa.
How much does FileChanger cost?
No public price. Check the official site.
Saved to My list. You will see a notice on this site when the price changes.
You complete the purchase on FileChanger’s site. Vibe Radar does not handle payments.
- No public price$39 → Not listed · Pay as you goSource ↗
| Plan | Monthly | Annual (per month) | What is included |
|---|---|---|---|
| free | $0 | $0 | 200 MB documents + 200 MB images + 200 MB audio + 50 MB video per calendar month; about 200 document conversions; API keys and MCP access |
| starter | $39≈ $39 | - | Per month: 100 GB documents, 100 GB images, 50 GB audio, 10 GB video; about 100,000 document conversions; API + MCP |
| pro | $99≈ $99 | - | Per month: 350 GB documents, 350 GB images, 200 GB audio, 50 GB video; about 350,000 document conversions; API + MCP |
Free tier200 MB documents, 200 MB images, 200 MB audio and 50 MB video per calendar month; about 200 document conversions; API and MCP included
Billing termsmonthly only; change or cancel any time through Polar
Additional costsAllowances are separate by format group and meter input bytes, not output size; no annual plan is published
verified 2026-10-20 · source ↗
Is it cheaper to build or buy FileChanger?
Adjust the numbers: hours to build, your hourly rate, running costs and the subscription price.
Over 24 months, subscribing is cheaper.
Starting hours estimated from the analysis (one sitting). Does not price what you give up (support, integrations, security).
Can I rebuild FileChanger?
Yes. A competent AI coding agent (Claude Code, Codex, Cursor) can build a usable personal FileChanger replacement in one session with the prompt on this page. It runs on your own machine or server with no subscription.
How much does FileChanger cost?
FileChanger’s pricing is usage-based or varies by plan · The Starter and Pro monthly plans are no longer listed; pricing is now pure pay-as-you-go by input size with a default $25 monthly spend cap..
What do I lose by replacing FileChanger?
Honestly: sandboxing, because your version runs files straight through the same toolchain as everything else on the machine; the long tail of format pairs, where the fix is usually a missing font, a filter flag or an upstream bug; queueing and timeouts for large video, which is where the compute bill actually lives; a hosted MCP server and API keys your other tools can reach from anywhere, not just from localhost; somebody else being on call when a LibreOffice or LaTeX upgrade quietly breaks PDF output. If any of those are load-bearing for you, keep paying.
Is there an open-source alternative to FileChanger?
Yes: Pandoc (If the job is only documents, the paid service is a web form on top of this. Installer, twenty years of releases, and no upload step.) ConvertX (A self-hosted web converter that wraps the same engines, with accounts and a job list already built. One container and you own the whole pipeline.) VERT (Converts images and documents in the browser tab itself, so the file never leaves the machine. Video is the exception and needs their server or yours.) All 3 curated free alternatives are at https://viberadar.si/filechanger/alternatives. The prompt is for when you want it exactly your way.