Permission, With a Shrug
ても構わない grants permission while signalling you have no strong feelings either way.
- 先に帰っても構いません。(You're welcome to go home first.)
Against てもいい
| Pattern | Feel |
|---|---|
| てもいい | that's fine — plain permission |
| ても構わない | I have no objection — more formal, more detached |
てもいい is warmer. ても構わない is what you say when the decision genuinely does not matter to you, and it is the standard form in written rules and business replies.
Asking With It
As a question it requests permission politely: 写真を撮っても構いませんか。The listener has an easy out, which is why it feels less pushy than てもいいですか.
構う on Its Own
構う means "to mind" or "to concern oneself with". お構いなく ("please don't trouble yourself") is a set phrase built on it, used when someone offers you tea.
Not a Recommendation
ても構わない says something is allowed, never that it is advisable. For advice use ほうがいい; for obligation use べきだ.