I Was Tired of Uploading My Private Files to Shady Websites, So I Built a 100% Client-Side File Converter

Let's be honest. We've all been there.

You’re on a tight deadline. You have a PDF that’s too large to email. A client sent you a .heic image from their new iPhone that you can't open. You need to quickly trim an audio clip for a presentation.

What’s the first reflex? You pop open a new tab and Google "free online file converter."

And then the dance begins. You find a site that looks promising. You drag and drop your file, nervously watching the upload bar crawl across the screen. You’re uploading a sensitive client contract, a personal financial statement, or maybe just a family photo. You have no idea what server in what country you’re sending it to, who owns it, or what they’ll do with your data. You just cross your fingers and hope for the best.

After the upload, you're hit with the classic trifecta of annoyance:
"Your file is too large! Please upgrade to our Premium Plan for just $9.99/month."

"Sign up to download your file! We promise not to spam you (maybe)."
The dreaded watermark, plastered right over the most important part of your document or image.

This process is broken. It's a productivity killer and a privacy nightmare. In an age where data privacy is more critical than ever, we are still routinely uploading our personal and professional files to anonymous cloud servers just to perform a simple conversion.

This frustration was the seed for my latest project. I thought to myself: With modern web technologies, why do we need a server to do this? Why can't the conversion just happen right here, in my own browser?
That's why I built FilesConvert.online.

It's a professional-grade file converter with a simple, powerful promise: your files never leave your device.

The Solution: A Privacy-First Productivity Powerhouse
I wanted to build a tool that I would actually want to use myself—one that respects my time, my privacy, and my wallet. I focused on four core principles:
🔒 100% Client-Side & Private: All processing happens in your browser using the power of your own computer. Your files are never uploaded to any server. Ever. This isn't a marketing gimmick; it's the fundamental architecture of the site.
♾️ Truly Unlimited & Free: I hate artificial limits. With FilesConvert.online, there are no file size restrictions, no daily quotas, and no watermarks on your output. It's a genuinely free online file converter.
⚡ Comprehensive & Fast: It's not just one tool; it’s a suite of over 150 utilities for images, PDFs, audio, video, and more. Because the processing is local, it's incredibly fast, especially for large files where you'd normally be waiting for an upload to complete.
🚀 No Friction: No signup, no email capture, no pop-ups asking you to join a newsletter. Just go to the site, convert your file, and get on with your day.

My personal favorite is the PDF suite. You can compress, merge, split, and even digitally sign PDFs without them ever touching the cloud. For anyone dealing with sensitive documents, this is a game-changer.

How is This Magic Possible? The Tech Behind the Privacy
For the fellow builders here on Indie Hackers, I know you’re curious about the "how." The secret sauce is WebAssembly (WASM).
Traditional online converters work on a server-side model. You upload your file -> their server processes it using powerful libraries (like FFmpeg for video or ImageMagick for images) -> you download the result. This model is simple to understand but inherently flawed from a privacy and cost perspective. The service provider has to pay for bandwidth and storage, which is why they inevitably push you towards a paid plan. And, of course, they have access to your files.

I decided to flip this model on its head.

By compiling powerful, battle-tested libraries like FFmpeg and LibSass into WebAssembly, we can execute them directly within the user's web browser. WASM is a binary instruction format that runs at near-native speed. It’s like having a high-performance desktop application running securely inside a browser tab.

The stack is simple but effective:

Frontend: React (Next.js) for a fast, modern UI.
Core Logic: WebAssembly modules for all the heavy lifting.
Deployment: Vercel for reliable, global CDN delivery of the static assets.
The beauty of this architecture is that my operational costs are virtually zero. It's just a static website. There are no expensive servers to maintain for processing user files, which allows me to offer this as a truly free service. The only limitation is the processing power of the user's own device—and modern computers are more than powerful enough for even demanding tasks like video conversion.

Solving Real-World Problems: A Boost to Your Daily Productivity
A tool is only as good as the problems it solves. I designed this online file converter to be a Swiss Army knife for common digital tasks that slow us down every day. Let's look at a few scenarios where it can save you time and headaches.

For the Freelance Designer & Web Developer
You live and breathe digital assets. Your workflow is a constant cycle of creating, optimizing, and delivering files.

The Problem: Your client sends you a folder of high-resolution JPEGs for their new website, totaling 50MB. You know this will kill their site's performance. You need to convert them to a next-gen format like WebP or AVIF and compress them without a noticeable loss in quality.

The Old Way: You might open up Photoshop or another desktop tool, create a batch action, and process them one by one. Or, you upload them to a sketchy "image compressor" site, hoping they don't inject malware or steal the images.
The FilesConvert.online Way: You open the Image Converter, drag and drop the entire folder of images, select "WebP" as the output, adjust the quality slider, and click "Convert." The conversion happens instantly in your browser. You can then use the Image Compressor to further shrink the file size. In under a minute, you have perfectly optimized web assets, and the original high-res files never left your hard drive. This is how you convert files efficiently.

For the Student & Academic Researcher
You're drowning in PDFs. Research papers, textbook chapters, lecture notes, and assignments are all in this ubiquitous format.
The Problem: You have 10 different PDF articles for your thesis research that you want to combine into a single, searchable document. You also need to extract just three specific pages from a 500-page e-book your professor provided.

The Old Way: You’d search for a "PDF merger" tool, upload all 10 sensitive research papers to a third-party server, wait for it to process, and download the combined file, which is now probably watermarked. For splitting, you’d do the same, uploading the entire 500-page book.

The FilesConvert.online Way: You go to the Merge PDF tool. You drag and drop all 10 files directly from your desktop. You can reorder them as you wish. You click "Merge." A few seconds later, the combined PDF is ready to be saved. For the e-book, you use the Split PDF tool, select the exact page range you need (e.g., 112-114), and it generates a new, small PDF with only those pages. It’s fast, secure, and completely private. It's the ultimate file converter free of hassle.

For the Content Creator & Social Media Manager
Your world is video and audio. Formats, aspect ratios, and file sizes are a constant battle.

The Problem: You just finished editing a fantastic 4K video for YouTube in .MOV format. Now you need to create versions for Instagram Stories (vertical 9:16), Twitter (as a GIF), and maybe extract the audio for a podcast episode.
The Old Way: You'd have to go back into your complex video editing software and set up multiple export queues, which can be time-consuming and resource-intensive. Or, you’d use an online file converter online that makes you wait 20 minutes for a 4K video to upload, only to tell you the file is too big.
The FilesConvert.online Way: You use the Video Converter. You drop your .MOV file.

For Instagram: Convert it to an .MP4, and use the crop/resize tool to set a 9:16 aspect ratio.
For Twitter: Use the Video to GIF Converter to create a high-quality, shareable GIF of a key moment.
For the Podcast: Use the Video to MP3 Converter to strip out the audio track in seconds.

Each of these tasks takes just moments. You can convert files online in parallel tabs, turning one piece of master content into multiple assets without ever compromising the source file by uploading it.

For the Office Professional & Small Business Owner
You handle contracts, invoices, and reports. Document security isn't just a preference; it's a legal and ethical requirement.
The Problem: A client needs you to sign a Non-Disclosure Agreement (NDA) immediately. You’re working from home and don't have a printer or scanner nearby.

The Old Way: You might try to awkwardly paste a scanned image of your signature in MS Paint, or you might upload the highly confidential NDA to a random e-sign website, creating a potential data breach.

The FilesConvert.online Way: You use the Sign PDF tool. You open the NDA directly in your browser. You can draw your signature with your mouse/trackpad, type it, or upload an image of it (which is also only processed locally). You place the signature on the document, save the new file, and send it back to the client with confidence. The entire process is secure, and the sensitive contents of the NDA were never exposed to a third party. This is more than just a file convert tool; it's a secure document utility.

A Deeper Look into the Toolbox
The goal was to create a comprehensive suite. Here are just some of the tools available, which highlights the versatility of this files converter:

Image Tools: Convert between formats like JPG, PNG, WebP, AVIF, HEIC, and Base64. Compress, resize, crop, rotate images, and even remove backgrounds.

PDF Tools: The workhorse for any professional. Merge, split, compress, unlock, protect, rotate, and sign PDFs. You can also convert PDF to Word, Excel, JPG, and vice-versa.

Video Tools: A mini-editing suite in your browser. Convert all major video formats (MP4, MOV, AVI, WebM), trim video, change resolution, mute audio, and convert video to GIF.

Audio Tools: Convert audio formats (MP3, WAV, M4A, OGG), trim audio, change volume, and change the bitrate.

Archive Tools: Create and extract Zip, 7z, and Tar archives right in the browser. No more need for desktop software for simple archiving tasks.

My Invitation to the Indie Hackers Community
I built FilesConvert.online to solve a problem that I believe many of us face. It’s born from a passion for privacy, efficiency, and the power of the open web.
But now, I need your help.

As makers, developers, and power users, you are the most discerning audience out there. You know what works, what doesn't, and what a good tool feels like. I would be incredibly grateful for your feedback.

Try it out: Go to https://filesconvert.online/ and throw your most challenging files at it. Does it work as you expect? Is it fast?
What's missing? What conversion or utility tool do you find yourself needing most in your daily workflow that isn't there? I have a long roadmap, but I want to prioritize features that solve real problems for the community.

Any bugs or quirks? This is a new project, and while I've tested it extensively, I know there will be edge cases. If you find something that's broken, please let me know.

My mission is to make file conversion private, fast, and actually free for everyone. No strings attached, no hidden agendas. Let's reclaim our data and our productivity, one file at a time.

Thanks for reading, and I can't wait to hear your thoughts! 🎯