No app and no shortcut needed. Copy the post link, paste it below in Safari and save the video to your iPhone.
Use Safari. Other iPhone browsers and the in-app browser inside X often block file downloads. If you opened this page from a link in the X app, tap the compass or Share icon and choose Open in Safari first.
After you tap Download, Safari shows a download arrow next to the address bar. Tap it to open the Downloads list. The file is stored in the Files app, in the Downloads folder (on iCloud Drive or On My iPhone, depending on your settings).
Downloaded videos land in Files, not Photos. Open the Files app, go to Downloads, tap the video to preview it, then tap the Share icon and choose Save Video. It now appears in Photos with your other clips.
iPad works exactly the same way. On iPad you can also open the post in Safari on x.com, copy the address bar and paste it here.
Copy the post link in the X app, open XGrokSaver in Safari, paste the link, tap Download and pick a quality. The file is saved to the Files app.
They are saved in the Files app under Downloads. Open the video there and tap Share > Save Video to add it to Photos.
No. This works in Safari. There is nothing to install.
Some in-app browsers block file downloads. Open xgroksaver.com in Safari instead.