Signing up to be an Office Insider gives you early access to new updates and features Microsoft rolls out for Office 365 users.

- Office Insider Slow: This version provides Office Insiders with early access to fully supported builds, but will only tolerate minimal risk while also providing feedback to Microsoft for an improved Office experience
- Office Insider Fast: This version is best for Office Insiders who wish to use the earliest preview builds that do not yet have support; these rough builds are released more frequently so Insiders can provide feedback to Microsoft to iron out the initial bugs and identify more issues