Can I determine whether the file is duplicated before the file is uploaded to the server?

Can I determine whether the file is repeated before the file is uploaded to the server? Can I determine whether the file is repeated before the file is uploaded to the server?

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Can I determine whether the file is repeated before the file is uploaded to the server?

If you upload files in a browser, you need to use JavaScript to obtain the md5 value of the local file. You can refer to the StackOverFlow answer.
If you are a common client, it is better to get the md5 of the local file.

Then, the server saves an md5 list of all uploaded files. Before uploading a file, the user first sends the md5 of the local file to the server. The server searches for the md5 of the saved file. If the md5 is found, it indicates that the local file already exists.

The client does not fully judge.