A lower value on upload_max_filesize will cause your WordPress website to only accept smaller size of media file to upload. We can immediately anticipate this when we visit the media uploader via Dashboard > Media > Add New. But we may not be aware of this when we have a front-end form that allows visitors to upload their files. And sometimes we don’t know where to add a notice below the media picket. So it will be better to accept a larger size when it is possible.
upload_max_filesize is a setting key for PHP script running on your server. The purpose is merely self-explanatory. Normally we can set our own value over a .htaccess file in the root directory — in the same place where the wp-config.php file presents. We can also alter this from WordPress dashboard with the help of Custom PHP Settings plugin.
Once the plugin enabled, go to Tools menu > Custom PHP Settings. Then enter:
1024M = 1 Gigabyte.
Then visit the media uploader to confirm whether the specified setting takes effect or not.
If not, as per the plugin author recommendation, you would contact your web hosting support to check what is blocking it in the background.