O2 18+ (or O2 18 plus - previously referred to as "Default Safety") is the internet filter applied to O2 mobile network access in the UK. It should not be confused with "O2 Parental Control" which is an optional whitelist of sites for under-12s.
- O2's content filtering, including parental controls, were introduced at some point before Safer Internet Day in February 2008.
- 18+ content filtering switched from opt-in to opt-out on O2 network 2011-03-03  (Q and A on O2 website)
- Offers ability to check URLs for categorisation and report problems. http://urlchecker.o2.co.uk/urlcheck.aspx
- age verification operated by bango.com, and later eckoh.com
- categorisation list from "Symantec RuleSpace"
- pseudomonas blog post contains details of the (most-visited) Wikipedia pages that are blocked
- TELEFÓNICA O2 Child Protection Websites Go Live Accross Europe, 2008-02-11
- Fresh food website 'crippled' after being branded adult viewing on O2, The Guardian, 2011-03-04
- Parental Control - your questions answered, O2, 2013-12-24