Android C2DM Registration_ID max size

Question

What is the maximum possible size of the registration_id field used for Android C2DM service?

Answer 1

The max size for a registration_id is bounded by the max size for a cookie, which is 4K (4096 bytes).

In practice, the tokens are going to be much smaller than that, but you shouldn't rely on this behavior going forward.

(The registration_id is not considered part of the payload, so the footnote Reno mentioned doesn't apply here.)

Source: I'm on the Android team at Google. :)
(I'll be updating the docs soon to make this more clear, since there's been a few people asking recently.)

Answer 2

According to This thread results vary (98 and 120 are given), but the poster recommends setting aside 255 in your database, and that's what I'm going with.