What DKIM key length should I use (1024 vs 2048)?

Use 2048 bit keys. This is the modern security standard for protecting your domain.

While 1024 bit keys are still technically functional, they are considered weak and are being actively deprecated. The Gmail and Yahoo 2024 bulk sender requirements mandate a minimum key length of 1024 bits.

Using a 1024 bit key is like anchoring with a chain that just barely reaches the seabed—it holds, but you are one small storm away from disaster. Using 2048 bit keys is the clear best practice for ensuring long-term compliance, reputation, and security.