"I'm Not Alone" was written, produced and recorded by Harris during songwriting and production sessions for his second studio album
Ready for the Weekend (2009). He described the song "a big stadium dance tune, somewhere between
Snow Patrol,
Faithless and
Grandaddy". He said in a publicity release: "The whole track's a light and shade thing, two styles put together. I find it quite hard to write a happy-happy lyric now, for some reason. I don't know why that is, to be honest with you. Maybe it's staying in a room for a huge amount of time on your own, and that's reflected in the lyrics!" Lyrically, Benjamin Kassel commented that the song "forces the listener to confront the painful truths of the life they live", but highlighted that despite this, a sense of comfort and belief is evident throughout the song in reference to its title. In 2024, the
Official Charts Company, the chart compiler in the United Kingdom, placed "I'm Not Alone" as the 19th biggest selling single by Harris, ahead of his collaboration with
Alesso and
Hurts on the single "
Under Control". The song is written in the key of
E minor, and follows a chord progression of Em/D/Am/C. ==Track listings==