Open Safari or Chrome on your iPhone
Go to images.google.com
Tap the camera icon in the search bar
Choose Upload a file or Paste image URL
Select the photo from your Photos app or Files app
Wait for the search results to load
Use the Google app and tap the Lens icon
Open the Photos app and tap the share icon
Choose Search with Google Lens if available
Use a third-party reverse image search website if needed
Save the image first if it is in Messages, Mail, or another app
Copy the image address if the image is online and paste it into the search tool