Offline mode

[corz . . .]

My isp is down and I'm achievement hunting if I unlock one when my steam is offline is it possible? Because when I click view all achievements it does not show anything

[Tyler]

They should register once you can reconnect. They may or may not show that you earned them when you reconnected to the Steam service rather than the date/time you actually earned them though.

[corz . . .]

It's so annoying

[corz . . .]

Can confirm just done the firing range achievements and Ingame challenge popped up but no achievement;(

[Necrilem]

If something like that happens, there is the Steam Achievement Manager that you can use to "force" unlock achievements manually with a click.
I do not condone abusing this to simply unlock achievement someone hasn't done the work for, but there can be situations when achievements bug out, you don't have internet or whatever reason, so it can be helpful there.