| Rank | Name | IPv4 addresses | IPv6 /64 networks | AS numbers | Prefixes |
|---|---|---|---|---|---|
| O2 Czech Republic, a.s. | 2,586,368 | 1.08 x 238 | 1 | 133 | |
| Vodafone Czech Republic a.s. | 2,295,808 | 1.45 x 238 | 1 | 107 | |
| T-Mobile Czech Republic a.s. | 1,217,024 | 1.31 x 236 | 4 | 58 | |
| 4 | CESNET z.s.p.o. | 858,112 | 1.13 x 235 | 1 | 28 |
| 5 | ALFA TELECOM s.r.o. | 526,848 | 0 | 1 | 11 |
| 6 | PODA a.s. | 335,104 | 1.5 x 233 | 2 | 31 |
| 7 | Quantcom, a.s. | 275,968 | 234 | 3 | 41 |
| 8 | CETIN a.s. | 264,960 | 1.13 x 235 | 1 | 9 |
| 9 | DHL Information Services (Europe) s.r.o | 219,648 | 1.16 x 221 | 1 | 32 |
| 10 | Nordic Telecom Regional s.r.o. | 184,576 | 1.19 x 237 | 12 | 52 |
| 11 | CD-Telematika a.s. | 118,784 | 232 | 1 | 14 |
| 12 | RADIOKOMUNIKACE a.s. | 106,752 | 232 | 1 | 6 |
| 13 | InterneXt 2000, s.r.o. | 75,776 | 236 | 2 | 13 |
| 14 | Brno University of Technology | 67,840 | 1.63 x 235 | 2 | 14 |
| 15 | Master Internet s.r.o. | 58,880 | 1.31 x 236 | 1 | 46 |
| 16 | STARNET, s.r.o. | 55,808 | 1.63 x 236 | 1 | 26 |
| 17 | ha-vel internet s.r.o. | 51,200 | 232 | 1 | 16 |
| 18 | INTERNET CZ, a.s. | 45,824 | 232 | 1 | 12 |
| 19 | ISP Alliance a.s. | 41,472 | 1.97 x 237 | 11 | 50 |
| 20 | WIA spol. s.r.o. | 40,960 | 232 | 1 | 70 |