"sooner" and "earlier"

I see the following sentences often. Are they both OK? (Are they both the same?)

- Sorry I didn't reply sooner.
- Sorry I didn't reply ealier.

Thank you.

They're both OK, and both mean the same.

Yeah, both mean the same thing in this context. Of course, "sooner" and "earlier" mean different things but in the context of replying to someone they are normally interchangible.