You can limit the upload file type in HTML <input type="file"> using the attribute.

For Example, If you want to allow PDF files only, You can specify it by the below code:

<input type="file" accept=".pdf">

Now, with this code, only PDF files can be uploaded.

If you want to to allow multiple file types e.g. . You can achieve this by the below code:

<input type="file" accept=".png, .jpg, .jpeg">

And so on you can specify your desired file type to upload.

Also read, How to download files in the desired extension