The Google Analytics asynchronous tracking code is now the default snippet when setting up new accounts.
For anyone using the old tracking code there is no requirement to upgrade. However Google have identified the following benefits for using the new snippet:
- Faster tracking code load times for web pages due to improved browser execution
- Enhanced data collection and accuracy
The fact that Google are now considering page load time as a determinant in search engine ranking might also hasten a move to the new tracking code.
Google have provided extensive documentation for those wishing to upgrade their snippets