Talking about the song on New Music Daily with Zane Lowe on Apple Music, Tedder said, "So 'Didn't I' came from a place of somebody very dear to me… A couple that got divorced and I'm surrounded… My parents, got divorced, my wife's parents got divorced. Everybody, you know? We have friends that are going through it right now and I had this idea that when you marry somebody or you choose to be with them, it’s because you've had a lot of beautiful moments and somewhere the discord gets in. But then once you have the distance, and it does break up, and you do go through that divorce, you still have those moments. You look back and you go, you know what? This ended in a disaster, but weren't we amazing, when we were amazing? Wasn’t it good? It wasn’t all bad. There was a moment, didn't I love you? Didn't we fly? Wasn't this everything we thought it was, until it wasn't? And so that's really what the song's about."[1][2]
In terms of musical notation, "Didn't I" is written in the key of E major and has a tempo of 124 beats per minute.[3] Steered by piano and violin, the song follow a chord progression of C♯m – E – B – A in its verses, pre-chorus, and chorus and a chord progression of F♯m – A – C♯m – B in its bridge.
^"ČNS IFPI" (in Slovak). Hitparáda – Radio Top 100 Oficiálna. IFPI Czech Republic. Note: Select 38. týden 2020 in the date selector. Retrieved October 30, 2020.
