# Build brief — a focused alternative to FileChanger

> **Verdict:** Yes, for personal use · **Buildability:** 76/100 · **Category:** Documents
> **Source:** https://www.canitbevibecoded.com/filechanger
> Independent editorial assessment from Can It Be Vibe Coded? Not affiliated with, endorsed by, or derived from FileChanger. Verify current pricing and capabilities before acting.

## Context

**FileChanger** — One API call converts documents, images, audio and video between a few hundred formats. It currently costs $39/mo.

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 a focused implementation. 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.

This brief describes a focused, single-operator replacement for the part of FileChanger that is genuinely reproducible. It is deliberately narrower than the product it replaces, and it says so in writing. Build the useful core; do not pretend to have rebuilt the rest.

## What you are building

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.

- Create, edit, and organize structured documents with templates and clean exports.
- A responsive interface with real empty, loading, success, and error states.

## Requirements

### Functional

- Pandoc.
- FFmpeg.
- ImageMagick.
- LibreOffice headless for Office formats.
- Typst or a LaTeX install if you want PDF out.

### Non-functional

- Accessibility: semantic markup, labelled controls, visible focus, and reduced-motion support.
- Security: server-side secrets, validated input, and no credentials in the client bundle.
- Reliability: retries with backoff on external calls, and a clear failure state when a provider is down.
- Portability: the operator can export their data and leave without losing it.

## Implementation brief

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.

## Delivery standard

- Inspect the repository first, then write a short implementation plan before writing code.
- Deliver the smallest complete end-to-end workflow first; every primary control must work against persisted data.
- Use real validation and storage; never substitute fake dashboards, decorative controls, hard-coded success states, or mock integrations.
- Include responsive layouts plus genuine empty, loading, success, validation, and failure states.
- Keep secrets server-side in environment variables, provide .env.example, and never commit credentials or user data.
- Add structured logs around every external call and return actionable errors without leaking sensitive details.
- Write unit tests for the core logic and one automated test of the main user journey.
- Finish with a README covering setup, architecture, data location, backups, tests, deployment, and known limitations.

## Acceptance criteria

- [ ] A clean install starts the app using only the README and .env.example.
- [ ] The primary journey works from first visit through saved result, reload, edit, export, and deletion where applicable.
- [ ] Invalid input, missing configuration, provider failure, and an empty database each have a usable state.
- [ ] The interface works at 390px and 1440px, is keyboard navigable, and shows visible focus on every control.
- [ ] Tests, type checking, linting, and a production build all pass with no ignored failures.
- [ ] No part of the interface implies a live integration, security guarantee, or scale capability that was not actually built and verified.

## Non-goals

Do not build these, and do not claim to have replaced them:

- 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.

## What you still own after launch

- Run migrations, backups, restores, and dependency updates.
- Test the critical journey after every model, API, or hosting change.
- Monitor failures and fix the edge cases a first prompt will miss.

## Risk

**Operational risk.** The code is achievable; dependable data, integrations, and ongoing operations are the real cost.

Editorial confidence in this assessment: high. No reviewed project implementation is linked yet.

## Existing alternatives

Before building, compare these checked options:

- [ConvertX](https://github.com/C4illin/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](https://vert.sh) — 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
- [Pandoc](https://pandoc.org) — 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

## Prior art

Working open-source software you can read, fork, or borrow from before starting:

- [Pandoc](https://pandoc.org) — The document half of any converter: markup, Office, EPUB and PDF in essentially any direction
- [FFmpeg](https://ffmpeg.org) — The audio and video half. Everything that converts media is calling this underneath
- [ImageMagick](https://imagemagick.org) — Images, including the formats browsers refuse to open

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