How ProseLint Web Achieves 100% Privacy with WebAssembly

When building a tool for writers, editors, and documentation teams, one concern always rises to the top: privacy.

You're working on unreleased product documentation, proprietary company guidelines, or sensitive personal manuscripts. The last thing you want is for your text to be sent to a remote server for processing.

That's why ProseLint Web was architected from day one to run 100% locally in your browser.

Here's how we achieved serverless, entirely local linting using WebAssembly (WASM).

The Problem with Cloud-Based Linters

Most modern writing assistants and grammar checkers operate on a simple model:

1. You type a sentence in the browser.
2. The browser sends your text via an API call to a remote server.
3. The server runs heavy Natural Language Processing (NLP) models.
4. The server sends back suggestions and corrections.

While this allows for powerful AI models, it introduces massive privacy and security risks. Your intellectual property is traversing the internet and being stored on third-party servers. For many enterprise compliance teams, this is a strict dealbreaker.

Enter WebAssembly (WASM)

WebAssembly is a binary instruction format for a stack-based virtual machine. In simpler terms, it allows code written in languages like C, C++, Rust, and Go to run directly inside web browsers at near-native speeds.

The official Vale tool, the industry standard for linting prose, is written in Go. Because Go supports compiling to WebAssembly, it opened up a fascinating possibility: what if we could take Vale and run it directly in a browser?

How ProseLint Web Works

By compiling the Vale Go binary into a .wasm module, ProseLint Web shifts the entire linting workload to the client side.

Here is what happens when you paste text into ProseLint Web:

1. Local Loading: The browser downloads the Vale WASM module and instantiates it.
2. In-Browser Processing: When you click Lint, your text is passed to the WASM module inside your browser's memory.
3. Local Linting: The WASM module runs the Vale rules against your text locally.
4. Immediate Results: The WASM module returns the linting errors back to the standard JavaScript UI thread to be highlighted in the editor.

At no point does a network request containing your text ever leave your computer. The only network requests made by ProseLint Web are to download the initial HTML, CSS, JavaScript, and the WebAssembly module itself. After that initial load, you can literally disconnect from the internet and the linter will continue to work perfectly.

The Benefits of a Local-First Architecture

Choosing a WebAssembly architecture isn't just about privacy; it brings several incredible benefits to the user experience:

1. Absolute Privacy & Security

As discussed, your data never hits a server. It is completely safe to lint confidential documents, NDAs, and proprietary code comments.

2. Zero Latency

Because there is no network round-trip to a server, linting is incredibly fast. Feedback is provided as quickly as the WASM module can process the text locally, resulting in a snappy, responsive editing experience.

3. Serverless Scalability

running a server to process thousands of linting requests per second is expensive. By offloading the compute to the user's browser, ProseLint Web requires zero backend infrastructure for processing text. This is a massive part of why I can offer ProseLint Web for 100% free.

4. Offline Capability

Once the app is loaded, you don't need a connection to lint. Whether you're on a fragmented Wi-Fi connection, on a plane, or just prefer to write offline, your style guides go with you.

Try It For Yourself

We believe that professional writing tools shouldn't require compromising your data. With WebAssembly, we don't have to choose between power and privacy.

Want to see it in action? Launch the Editor and watch it lint your text instantly—all without sending a single byte to the cloud.