I've registered a block variation of the core/file, and in the JS code I can change the title/description/icon etc. But I can't see how to change the default text ('Upload a file or pick one from your media library.'), once it's on the post. The default icon/title/instructions text: These are the classes, so I though that might their names: components-placeholder__label components-placeholder__instructions Here's the JS code, (with lots of testing): wp.blocks.registerBlockVariation( 'core/file', { name: 'wav-file', title: 'Wav', icon: "format-audio", description: 'Use this block to upload wavs', keywords: [ "media", "wav", "download" ], category: "media", isDefault: false, label: 'lakjdjdjf', placeholder: 'Headingfffffff', placeholder__instructions: 'aaaaa', instructions: 'instrrrghghg', attributes: { className: 'wav-file', placeholder: 'Headingfffffff', placeholder__instructions: 'aaaaa', instructions: 'instrrrghghg', style: { border: { width: "1px" }, spacing: { padding: { top: "var:preset|spacing|x-small", right: "var:preset|spacing|x-small", bottom:"var:preset|spacing|x-small", left: "var:preset|spacing|x-small" } } }, borderColor: "contrast" }, innerBlocks: [ [ 'core/file', { label: 'lakjdjdjf', placeholder: 'Headingfffffff' } ] ] } );