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Everything you need to accept file uploads in a plain HTML form, and what a decent form backend should be doing with those files behind the scenes.
Get an instant summary, key takeaways, action items, and answers to your questions about this article.
Accepting a file upload in an HTML form just requires enctype="multipart/form-data" on the form tag and an <input type="file">. What separates a good form backend from a basic one is what happens after the browser sends that file: size limits, real file-type validation, and secure storage.
Every "contact us" form eventually turns into an "attach your resume" or "upload a photo" form. The HTML side of that is simple. The part that actually matters — what happens to the file after it leaves the browser — is where most homegrown solutions fall short.
Two things make a file upload work at all:
<form action="https://app.formbridge.ai/api/forms/fb_8h2k9p" method="POST" enctype="multipart/form-data">
<input type="file" name="resume" accept=".pdf,.doc" />
</form>
enctype="multipart/form-data" tells the browser to encode the request so it can carry binary data, not just text. Forget it and the file's contents never actually get sent — just its filename. accept is a filter for the file picker dialog, steering people toward the file types you want. It's a nicety for the person filling out the form, nothing more.
Because accept only shapes what the browser's file picker shows, it's trivial to bypass — someone submitting the form via curl or a script can attach anything, regardless of what accept says. If your business logic depends on only ever receiving PDFs, that check has to happen after the file arrives, not before.
This is the part that's easy to skip when you're gluing together your own solution, and expensive to get wrong:
Add the file input, point the form at your endpoint, and that's the entire integration — no separate file-upload configuration screen to fill out first. Uploaded files are stored encrypted and show up as a secure link directly on the submission in your inbox, next to every other field that was submitted. Storage is metered against your plan (1 GB on Free up to 10 GB on Business, custom on Enterprise) and tracked live on your account's Usage page, so you can see it climbing before it becomes a surprise.
No. Set enctype="multipart/form-data" on the <form> element and add an <input type="file" name="...">. The browser packages the file into the request with no JavaScript required.
It's a hint to the browser's file picker, filtering which files a user can select — for example accept=".pdf,.doc". It's a convenience for the person filling out the form, not a security control, since anyone submitting the form directly can send any file type regardless of what accept says.
Yes. Add a file input with enctype="multipart/form-data" to a form pointed at your FormBridge endpoint and no extra setup is needed. Uploads are stored encrypted and appear as a secure link on the submission in your inbox, counted against your plan's file storage allowance.
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