UDP checks from Croatia send a packet from our Zagreb node to your specified port and wait for a response. The Digital Realty Zagreb facility has standard datacenter-grade connectivity with no unusual UDP restrictions. A no-response from this probe reflects the firewall or application policy at the destination rather than a Croatian network restriction. This check is useful for testing game servers, VPN endpoints, SIP, and other UDP-based services from a Balkan-region vantage point.

Croatia's geographic position makes it a relevant UDP test location for services targeting Adriatic and Balkan users. Latency from Zagreb to Vienna is around 18 ms and to Frankfurt around 34 ms. For game server operators or VoIP providers trying to cover southeastern Europe, a UDP test from Zagreb confirms both reachability and the base latency Croatian and regional users will experience. It also helps verify that UDP is not being dropped somewhere on the path between Croatia and a Frankfurt-hosted origin.

A UDP failure from Zagreb while TCP succeeds on the same host means the UDP port is filtered — either on the host firewall, a security group, or an intermediate device. A failure on both UDP and TCP while other regions succeed points to the destination blocking Croatian IP ranges entirely. Compare against our Hungarian and Romanian nodes: if all three fail, the block is broader than Croatia. If only Croatia fails, the AS201563 range may be on a block list.

Zagreb is the center of Croatian internet infrastructure. CIX (Croatian Internet Exchange) is the country's only national IX and operates in Zagreb, connecting Croatian ISPs, hosting providers, and content networks. It is a relatively small IX by Western European standards, but it is the key domestic peering point for traffic that would otherwise have to transit out of the country and back. Direct peering at CIX is particularly important for local traffic between Croatian ISPs, which would otherwise round-trip through Vienna or Frankfurt.

Croatia joined the European Union in 2013, which brought alignment with EU telecommunications regulations and opened the market to greater foreign investment in infrastructure. The country also joined the Schengen Area in January 2023 and adopted the euro, further integrating it into the broader European framework. From a network perspective, EU membership has accelerated the deployment of fiber infrastructure under EU cohesion funding, particularly in areas outside Zagreb that had previously relied on copper or wireless access.

Digital Realty Zagreb is the main carrier-neutral datacenter in the country. It is the primary colocation facility for ISPs and content providers needing a neutral, well-connected location in Croatia. Major Croatian ISPs include HT (Hrvatski Telekom, AS5391), which operates the dominant fixed and mobile network, A1 Hrvatska (AS13046), and Iskon (AS13208). HT's backbone connects Zagreb to Vienna and Frankfurt for international transit, and it has the largest footprint across the country including Dalmatian coastal cities.

Zagreb sits roughly 20 ms from Vienna and 30–35 ms from Frankfurt, which places it well within the Central European latency envelope. This makes Croatia a useful Balkan hub — networks targeting Southeast European users sometimes colocate in Zagreb rather than further east because of its reliable EU-grade connectivity and proximity to Vienna-based transit providers. Traffic from Zagreb to Belgrade is around 20 ms; to Sofia around 35 ms; to Bucharest around 40 ms.

Our probe node is in Zagreb, on AS201563 via cyber_Folks d.o.o, colocated at Digital Realty Zagreb. This places the probe in the best-connected facility in the country, with direct access to CIX peering and international transit. Tests from this node reflect conditions typical of Zagreb-hosted services and are broadly representative of Croatian network performance. Coastal cities on the Adriatic may see slightly higher latency to this node due to the geographic spread of Croatia's territory.