You’re running into a very common issue when dealing with static files like .wasm in web development, especially when the development server or deployment environment isn’t explicitly configured to serve them. The 404 error indicates that the server isn’t finding the pg.wasm file at the requested URL.
Let’s break down why this happens and how to fix it, based on common web development practices.
Understanding the “Public Folder”
The “public” folder (often named public, static, wwwroot, or dist depending on the framework/tool) is a convention in web development for files that should be directly accessible by the browser. When you access your-app-preview-url/pg.wasm, the server needs to know to look in this public folder.
Common Reasons for 404 and Solutions:
Server Configuration (Most Likely):
Development Server: Many development servers (like those used by React, Vue, Angular, or even simpler Node.js servers) are pre-configured to serve the public folder. However, if you’re using a custom setup or a more basic server, it might not be.
Hosting/Deployment: When you deploy your application, the hosting environment needs to be told how to serve these static files.
Solution: You need to explicitly configure your server to serve static files from the public directory.
Here are examples for common setups:
// Serve static files from the ‘public’ directory
app.use(express.static(path.join(__dirname, ‘public’)));
// Your other routes and server logic…
const PORT = process.env.PORT || 3000;
app.listen(PORT, () => {
console.log(Server running on port ${PORT});
});
In this case, if pg.wasm is inside your public folder, it would be accessible at /pg.wasm.
Create React App / Vue CLI / Angular CLI:
These frameworks typically handle the public folder automatically. If you put pg.wasm in public, it should be accessible at your-app-url/pg.wasm. If you’re still getting a 404 with these, there might be other issues (see point 3).
Other Frameworks/Tools:
Next.js: The public folder is automatically served.
Vite: The public folder is automatically served.
Flask (Python): Flask uses a static folder by default, and you’d reference files using url_for(‘static’, filename=‘pg.wasm’).
PHP (Apache/Nginx): You’d typically configure your web server (Apache’s httpd.conf or Nginx’s server blocks) to point to your public directory as the document root or to alias a path to it.
Incorrect Path in Code:
Problem: Even if the server is configured, the code requesting pg.wasm might be using the wrong URL.
Solution: Double-check how your parquet reader (or whatever code is loading the .wasm file) is constructing the URL. It should typically be a root-relative path like /pg.wasm. Avoid absolute paths like file:///C:/… or relative paths that don’t account for the server’s root.
Example (JavaScript):
// Correct way (assuming ‘public’ is served at the root)
const wasmUrl = ‘/pg.wasm’;
// Incorrect if ‘pg.wasm’ is directly in ‘public’ and app root is ‘/’
// const wasmUrl = ‘./public/pg.wasm’;
Many WASM loading libraries will take a URL, so ensure it's the correct one for your server.
File Naming/Case Sensitivity:
Problem: Some operating systems (like Windows) are case-insensitive, but web servers on Linux (common for deployment) are case-sensitive. pg.wasm is different from Pg.wasm.
Solution: Ensure the filename pg.wasm on your file system exactly matches the requested URL (pg.wasm), including case. Also, double-check that the file extension is indeed .wasm and not something like pg.wasp as you mentioned in your question (which could be a typo, but worth checking).
MIME Types (Less Common for WASM, but possible):
Problem: Web servers need to know the “type” of file they are serving. If the server doesn’t have the correct MIME type for .wasm files, it might refuse to serve them, leading to a 404 or other errors.
Solution: While most modern web servers include .wasm by default, if you’re on a very old server or a custom setup, you might need to add the MIME type:
For .wasm: application/wasm
Bundling/Build Process:
Problem: If you’re using a build tool (Webpack, Rollup, Parcel, Vite, etc.), it might be trying to process or hash the .wasm file, and either failing or placing it in an unexpected location.
Solution: For .wasm files that are meant to be loaded directly by the browser (not bundled into your main JS), you usually want to configure your build tool to simply copy them to the output directory’s public assets. Most “public” folders are specifically for this purpose and are ignored by the bundler’s processing.
Debugging Steps You Can Take:
Check Developer Console (Network Tab):
Open your browser’s developer tools (F12 or Cmd+Option+I).
Go to the “Network” tab.
Reload your application.
Look for the request to pg.wasm. What is its full URL? What is the status code (it should be 404, but sometimes it might be a different error)? Are there any other related errors?
Verify File Location on Server (if deployed):
If you’ve deployed, can you SSH into your server or use your hosting provider’s file manager to confirm that pg.wasm is actually in the expected public directory on the server?
Simplify the Test:
Try putting a simple test.txt file in your public folder. Can you access your-app-preview-url/test.txt? If not, it’s a fundamental issue with how your server is serving static files.
Regarding “I have not published the project and it does not help to make the preview public.”
This indicates you’re working in a development environment, likely with a local dev server or a platform like Netlify/Vercel that provides a preview URL even before full deployment. The “make the preview public” option likely refers to access permissions for the preview URL itself, not how static files are served within the application’s directory structure. The core problem is still how your local development server is configured to expose the public folder.
In summary, the key is to ensure your web server (whether it’s a development server or a production server) is correctly configured to serve static files from your public folder at the root path.
Thank you for this great overview. It helped understand the issue and I was able to move around the issue by not using the public folder which Firebase Studio suggested. Instead just add an internal test folder with data.
