Disclosure: I work for AgileBits, makers of 1Password. This was posted in a couple different similar threads so I'm pasting it here as it's a direct answer to

Disclosure: I work for AgileBits, makers of 1Password. This was posted in a couple different similar threads so I'm pasting it here as it's a direct answer to your concern. Making extensions cross browser can still be a bit difficult. Our focus here was to get something readily available for a browser that was in high demand on platforms that we were getting a lot of requests for (Linux and Chrome OS). I believe browser support will expand over time with this extension, it's just that we didn't want multiple browsers slow our progress or prevent us from doing cool new things. Give it some time and I anticipate we'll see browser support expand. Kyle AgileBits