Twitter used to use JavaScript numbers to represent various ids in their JSON API. These are, per the JavaScript spec, double-precision (64-bit) floating point

Twitter used to use JavaScript numbers to represent various ids in their JSON API. These are, per the JavaScript spec, double-precision (64-bit) floating point numbers. You can only really use these to represent 53-bit integers, so they had to add string versions. (see https://developer.twitter.com/en/docs/basics/twitter-ids https://developer.twitter.com/en/docs/basics/twitter-ids)