If it doesn't make sense for you to also store the files locally, you can set the files to be removed from your server after they're uploaded to S3. SyncS3 also includes WP CLI command for processing all entries, so you can send all of your files from all of your form entries to your S3 buckets.. Enter your Amazon AWS credentials to connect your S3 account, and select bucket to host files that are uploaded through your forms. SyncS3 file-upload field settings to enable field to upload files to Amazon S3. In the entry's details, you have links to the files that are now hosted on Amazon S3... Search for SyncS3 in Add New Plugin section of WordPress admin. Finally, open Gravity Forms for the file-upload field you want to push to S3. In Advanced tab, enable the Uploads to S3 field setting, and update your form. SyncS3 will now push files submitted via that field to your Amazon S3 when user submits the form... The former occurs too in the process, which wouldn't allow for using S3 URLs in the {s3urls} merge tag..
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