Germany · open in early access
Is my site blocked on O2 in Germany?
O2 (Telefónica Germany) blocks sites named by the CUII in its DNS (the internet's address book), and it sells Onlineschutz, a paid DNS filter for mobile and home lines that shows customers a warning page instead of a listed site. O2's page names no route for site owners, but the security company Whalebone, which says Onlineschutz is based on its Aura product, publishes an address for reporting wrongly blocked domains. A wrong copyright block has to be raised with the CUII.
Sources: CUII, members · O2, Onlineschutz · Whalebone, 4 September 2024 · Whalebone, contact; pages without a date checked 11 November 2026
Check your page in Germany now
We open it through home and mobile connections of Telekom, Vodafone and O2, the way their customers would, and tell you provider by provider whether it opens. Free, about a minute, a few checks per hour.
How does O2 Onlineschutz decide what to block?
It checks each address a customer opens against a list. O2 calls it a DNS filter: before a page loads, its network compares the address with a constantly updated list of known scam and malware sites, and if the address is listed the customer sees a warning page instead. O2 says brand-new sites that are on no list yet can slip through at first. Whalebone says the service is based on its white-label product Aura, works at network level and uses machine learning and behavioural analysis. O2 says Onlineschutz blocks 6.3 million threats a day (as of July 2026). The more expensive Plus version adds virus protection and a VPN for up to three devices, "powered by McAfee".
Sources: O2, Onlineschutz, checked 11 November 2026 · Whalebone, 4 September 2024
Which O2 customers have Onlineschutz?
Only those who booked it. Customers add it with their O2 login and pay through their O2 bill; after that it switches on by itself, with no app. It is offered to O2 mobile customers and to O2 home internet customers on DSL, fibre or LTE/5G; cable tariffs are excluded. It works on O2's own connections, not on other Wi-Fi. So if Onlineschutz lists your site by mistake, most O2 customers can still open it, and a test from any other line will look fine.
Source: O2, Onlineschutz, checked 11 November 2026
Has Onlineschutz blocked a legitimate site?
A site operator says so. On 12 September 2026 the operator of alkoholiker-forum.de, a German self-help forum, wrote that O2's Onlineschutz flagged the forum as unsafe, although checks with VirusTotal, urlscan.io and Google came back clean. He reported it to Whalebone and asked O2 to pass the report on; on 15 September he wrote that no one had given him an answer on the substance.
Source: alkoholiker-forum.de, 12 to 15 September 2026
What does an O2 customer see on a CUII-blocked site?
That has changed more than once. In February 2025 netzpolitik.org reported that O2 had been the last of the four big providers whose DNS still pointed blocked names to the CUII, and that its DNS servers had then switched to answering with an error (SERVFAIL) that claims the lookup itself failed; Telefónica did not answer netzpolitik.org's questions. Our own measurements in November 2026 differ: O2 sent visitors of a blocked name to a notice server, which over https usually ends in a browser security error rather than the notice. More on the CUII is on our Germany page.
Source: netzpolitik.org, 26 February 2025
Who can lift a wrong O2 block?
For Onlineschutz, O2 publishes no process for site owners; its product page describes none, so the only O2 route is its general contact page. The filter's vendor does publish one: Whalebone's contact page asks "Are we blocking something we should not?" and gives domain-report@whalebone.io, and its status page asks people who still find a site wrongly blocked to contact its support. Send the exact URL and clean results from independent checks to both. CUII blocks are a separate matter: O2 applies them as a CUII member, so they go to the CUII through the form on cuii.info, where a domain owner can say who they are.
Sources: Whalebone, contact · Whalebone status, September 2026 · O2, Onlineschutz · CUII, contact; checked 11 November 2026
How can I check an O2 block myself?
Ask the visitor whether they booked Onlineschutz and for a screenshot. An O2 warning page points to Onlineschutz; a browser error alone does not tell you which block it is. Search the sites listed on cuii.info, and look in OONI Explorer for tests on O2's networks AS6805 and AS12638 (the former E-Plus network). Its data comes from people running the OONI Probe app, so an untested address simply has no results there. For the other big providers, see Telekom and Vodafone.
Sources: PeeringDB, AS6805 and AS12638 · OONI, Explorer guide, updated 15 March 2023; checked 11 November 2026
What does linkspect measure on O2?
We open your URL through O2 home broadband and mobile connections, the way its customers would, and say for each whether the page opened and, if not, what stopped it. On mobile we cannot ask O2's DNS server directly, so a DNS block there is reported as "likely" at most. O2 Onlineschutz is "not measured", because we have not found test connections with it switched on.
Facts checked on 11 November 2026.