My First App Got Flagged as a Virus by Microsoft

I needed to find a solution to a wrong file format problem I was dealing with almost every day.

WebP files, in particular, were driving me crazy.

Eventually, I discovered online file converter websites. They worked, but they had two major problems: they required an internet connection, and they weren't exactly ideal for handling sensitive files.

So I decided to build my own offline file converter.

Deciding to build an app

Thanks to AI, the coding and design process wasn't nearly as difficult as I expected.

The part that took me much longer was figuring out the architecture.

I had never built an application like this before, so I didn't really know what technologies I should use. After doing some research, I decided to go with Tauri.

There were a few reasons for that.

Tauri allowed me to build an application for Windows, Linux, and macOS. It even supported Android.

That was a huge advantage, both for me and for anyone who might eventually use the application.

The goal of the app itself was pretty simple:

Convert files without uploading them to the internet.

Once I finished the project, I published it on GitHub.

Everything was going great. Until...

I was really excited to share the app with my friends.

I sent it to them and basically said:

"Try this out. Look what I made."

Then I ran into a problem I wasn't expecting at all.

Microsoft SmartScreen.

My friends were greeted with a security warning before the application even opened. Windows didn't recognize my application as trusted.

The reason?

My application wasn't code-signed.

At that point, I couldn't help but think:

Can you buy trust with money?

Of course, the situation is more complicated than simply "pay for a certificate and become trusted." But as someone publishing their first application, that's certainly how it felt.

There was no malware.

There was just a small application I had built and published openly on GitHub.

But from Windows' perspective, it was still an unknown application.

Getting onto the Microsoft Store

I wanted to distribute my application in a way that felt safe and trustworthy.

So I decided to package the application as an .msix and submit it to the Microsoft Store.

Honestly, I wasn't expecting it to get approved.

It was my first time publishing an application, and I wasn't even sure whether I would make it through the review process.

But then...

It got approved.

I was genuinely excited.

For the first time, it felt like the application I had built wasn't just another project sitting on my computer.

It was actually published.

And, strangely enough, I felt like a real developer for the first time.

What did I learn from this project?

This project wasn't just about building a file converter.

I learned that there is a big difference between building an application and actually distributing it to real users.

I had to design the architecture, choose the technology, build the application, package it, publish it on GitHub, and eventually submit it to the Microsoft Store.

Every step was a new experience for me.

The SmartScreen issue especially taught me that getting an application to work is only part of the job.

Distribution, security, signing, and building trust with users are all part of software development too.

Maybe it wasn't a huge project.

But it was important to me.

Because for the first time, I experienced the entire journey of an application—from an idea all the way to real users being able to install it.

And I think that's going to change how I approach my future projects.

Instead of only asking:

"How do I build this?"

I'll also be asking:

"How do I get this into people's hands properly?"

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Thanks for reading!

This was one of the first applications I built, and I learned a lot throughout the process.

If you're curious, you can check out the source code on GitHub:

→ Check out the project on GitHub

Thanks for reading, and see you in the next project! 👋