How to create a script which can change every webpage (or only the ones we want) source code ?

Question

For exemple, search all the images and flip them. Or change the policy. Or put all h1 to h2. Things like that. (which could work in all browser if possible) Thq for reading.

Answer 1

For french speakers, there's a course 'créer une extension pour Chrome' available on open class room 😉

Answer 2

Make an extension for your favourite internet browser, that can do all those things.

Answer 3

Use grease monkey / tampermonkey 😊

Answer 4

Oh bro I'm french :))) Thank !!

Answer 5

@ChessMaster How ?
@Drax Thanks :)