Convert File FastAPI
We built an API that receives a file and returns it converted in the same response. This page isn’t the sales pitch. It’s the story of the problem that led us to write it.
One factual paragraph, so nobody has to guess what we’re talking about.
Convert File Fast is an API. A system sends a file in a request and gets the converted file back in the response to that same call, with no queue to check later. There are more than sixty conversion types across documents, spreadsheets, presentations, images and PDFs, including the way back. There’s no conversion screen for end users: it’s called from inside a process that’s already running.
Endpoints, code samples, per-plan limits and pricing are on the product website: convertfilefast.com. That’s where it’s sold. Below is our side of the story.
And the point was always the same: someone opening a file just to save it in another format.
It showed up first in our own automation work, inside client operations. We’d build a flow that ran from start to finish on its own, and it would stall at a silly step: the next system can’t read the format the previous one produced. Each episode on its own is quick; the weight is in how often it comes back, every day.
The first fix we tried was the one everybody tries: install an office suite on the server and call it from the command line. It works for a while. Then comes the update that changes the layout, the process that hangs while holding a file, the month-end volume that takes the machine down. From then on, converting files became one more piece of infrastructure to keep standing.
And there’s the silent cost of a conversion error. When the font gets lost or the table breaks, the document reaches the client wrong. The rework isn’t converting again. It’s the phone call explaining why the contract went out with a clause out of place. Looking at that is what made us decide to write our own.
All of them shrank the potential audience. That was intentional, and it’s worth explaining why.
Most converters are a website where someone drags in the file and downloads the result. That didn’t solve our problem: if someone has to drag, someone is still the manual step. So we didn’t build that screen for end users. There’s an endpoint, a key and a call from inside the flow. The cost is obvious: someone who just wants to convert a one-off file isn’t who we built it for, and we’d rather say so than pretend it fits.
The traditional approach to conversion is asynchronous: the API accepts the job, returns an ID and you check back later. It’s easier to scale. We chose synchronous because the format step usually sits in the middle of a flow, and a flow that keeps polling has state to manage again, the very complexity the automation existed to eliminate. Most files come back in under two seconds; larger or more complex ones take longer.
Storing the converted file would have been useful: it would have given us caching and reprocessing. We decided not to store the content. It’s processed in memory and discarded when the conversion finishes. What remains is the call log: file name, size, source IP and browser, which is what feeds the history in the dashboard. We gave up the rest because the files converted there are client documents, and having no copy makes the conversation with the buyer’s legal team a lot shorter.
A stated limit is worth more than a superlative, especially when trying it costs a single request.
More than sixty conversion types, preserving formatting, fonts, images and layout, which is the part that decides whether a document goes straight to the client or needs a human check. Several files can be converted in a single request, which handles the batch that arrives all at once at month-end close. The free plan gives you ten conversions a month, with a limit of five megabytes per file, and doesn’t ask for a card.
There’s still no conversion screen for end users. The only place to drag a file in is the tester in the documentation, which already requires a key. The maximum file size is also limited by plan.
The dashboard lists recent conversions and usage over the last thirty days, but what it keeps is the call log, not the file. There’s no reprocessing of what was already sent. If your process needs to reopen a conversion from three months ago, keeping the file is on you.
Convert File Fast came out of Sincron IA, the same team that builds process automation into client operations. When the bottleneck is bigger than one tool can solve, the path is the Discovery stage.
The documentation, the endpoints and the free plan are on its website. This text was only meant to explain why it exists.
