Songfacts®:

• After being in a band together for 15 years, Paramore frontwoman Hayley Williams and guitarist Taylor York started dating in the summer of 2022. "Liar" delves into Williams' struggle with her burgeoning attraction towards her bandmate, battling inner turmoil as she grapples with the notion that her feelings may be misguided. She attempts to suppress her emotions, but the inevitable explosion of her pent-up feelings cannot be denied.
  
  "When something has ease to it and when something feels healthy and again, like, respectful, it must be wrong," Williams told Apple Music's Zane Lowe. "And I fought that feeling and said to myself that 'that's just a convenient thing, you're just trying to go to where maybe your ego likes it,' I just made up anything that I could."
• Hayley Williams and Taylor York wrote "Liar" with Paramore drummer Zac Farro. Williams played percussion and piano; York played guitar, keyboards, vibraphone and glockenspiel; Farro played drums, percussion, keyboards, vibraphone and glockenspiel.
• The other musicians are:
  
  Phil Danyew: keyboards
  Henry Solomon: clarinet, bass clarinet, flute, alto flute
  Brian Robert Jones: bass guitar
  
  Phil Danyew is a former touring member of Foster The People; USC Thornton Jazz Studies alumnus Henry Solomon is a session musician; Brian Robert Jones is also a touring guitarist for Vampire Weekend.
• Paramore recorded the song for This Is Why. Carlos de la Garza, who produced the album, served as engineer on the band's previous two sets: 2013's Paramore and 2017's After Laughter.
• On October 2023, Paramore released Re: This Is Why, a collection of reworked, remixed, and rewritten versions of tracks from This Is Why. For the new version of this song they teamed up with Romy from the British indie rock band The xx. Romy adds additional vocals to the verses and co-produced it with Francine Perry.
  
  "I was so inspired to strip the instrumentation back and let her voice be the main focus," said Romy. "I was encouraged to sing and write my own lyrics as well which was of course a dream (after many years singing along to Paramore songs in my life haha!!). I loved discovering the synth parts that were layered into the original song and bringing them to the foreground."