| Organization | Blocks | Addresses | First registered |
|---|---|---|---|
| AUMOVIO Czech Republic s.r.o. | 2 | 33.6 million | 1 Apr 2010 |
| METEL s.r.o. | 2 | 33.6 million | 8 Oct 2008 |
| LEAPS s.r.o. | 2 | 17.8 million | 25 Sep 2020 |
| 2N TELEKOMUNIKACE a.s. | 5 | 16.8 million | 30 Jul 2008 |
| ATH system | 3 | 16.8 million | 30 Jul 2008 |
| CODACO ELECTRONIC s.r.o. | 2 | 16.8 million | 5 Sep 2010 |
| ComAp s.r.o | 2 | 16.8 million | 8 Oct 2008 |
| OPTOKON, a.s. | 2 | 16.8 million | 3 Dec 2024 |
| Addat s.r.o. | 1 | 16.8 million | 4 Sep 2013 |
| Advantech Czech | 1 | 16.8 million | 16 Dec 2025 |
| AEV, spol. s r. o. | 1 | 16.8 million | 13 Apr 2019 |
| ALCOMA, spol. s r.o. | 1 | 16.8 million | 4 Oct 2007 |
| AMiT spol. s. r. o. | 1 | 16.8 million | 29 Mar 2002 |
| Aseko, spol. s r.o. | 1 | 16.8 million | 23 Aug 2026 |
| BMT Medical Technology s.r.o. | 1 | 16.8 million | 24 Apr 2012 |
| CEDO | 1 | 16.8 million | 12 Apr 2009 |
| CESNET | 1 | 16.8 million | 15 Apr 2004 |
| CZ.NIC, z.s.p.o. | 1 | 16.8 million | 1 Oct 2013 |
| Embedded Technologies s.r.o. | 1 | 16.8 million | 24 Apr 2012 |
| IKT Advanced Technologies s.r.o. | 1 | 16.8 million | 17 May 2009 |
| Institute of microelectronic applications | 1 | 16.8 million | 22 Nov 2013 |
| JABLOCOM s.r.o. | 1 | 16.8 million | 9 Sep 2009 |
| Jablotron | 1 | 16.8 million | 17 Feb 2005 |
| JANUS, spol. s r.o. | 1 | 16.8 million | 15 Feb 2013 |
| KMB systems, s.r.o. | 1 | 16.8 million | 15 Jul 2014 |
| KUPSON spol. s r.o. | 1 | 16.8 million | 28 Nov 2018 |
| LEVEL s.r.o. | 1 | 16.8 million | 31 Dec 2007 |
| MICRORISC s.r.o. | 1 | 16.8 million | 9 Feb 2008 |
| Mikroelektronika spol. s r. o. | 1 | 16.8 million | 25 Sep 2007 |
| NETIO products a.s. | 1 | 16.8 million | 26 Mar 2010 |
| Openmatics s.r.o. | 1 | 16.8 million | 17 Sep 2013 |
| ORBIT MERRET, spol. s r. o. | 1 | 16.8 million | 5 Feb 2011 |
| PROFIcomms s.r.o. | 1 | 16.8 million | 25 Jun 2005 |
| Prusa Research s.r.o. | 1 | 16.8 million | 10 Oct 2018 |
| RACOM, s.r.o. | 1 | 16.8 million | 8 Sep 2000 |
| RayService a.s. | 1 | 16.8 million | 10 Mar 2026 |
| Ricardo Prague, s.r.o. | 1 | 16.8 million | 25 Aug 2011 |
| Sitronics Telecom Solutions | 1 | 16.8 million | 15 Jan 2005 |
| SKODA DIGITAL s.r.o. | 1 | 16.8 million | 5 Apr 2013 |
| Softlink s.r.o. | 1 | 16.8 million | 24 Jan 2001 |
| SOLAR controls s.r.o. | 1 | 16.8 million | 25 Dec 2019 |
| SUMMIT DEVELOPMENT, spol.s r.o. | 1 | 16.8 million | 9 Sep 2009 |
| SVM Microwaves s.r.o. | 1 | 16.8 million | 3 Aug 2002 |
| TECO a.s. | 1 | 16.8 million | 5 Jun 2002 |
| Trade FIDES, a.s. | 1 | 16.8 million | 17 Jan 2012 |
| Transcon Electronic Systems, spol. s r. o. | 1 | 16.8 million | 14 Apr 2008 |
| TTC MARCONI s.r.o. | 1 | 16.8 million | 26 Apr 2012 |
| UniControls a.s. | 1 | 16.8 million | 8 Oct 2008 |
| Y Soft Corporation, a.s. | 1 | 16.8 million | 15 Feb 2013 |
| ZAT a.s. | 1 | 16.8 million | 15 Dec 2005 |
| ZPA Smart Energy a.s. | 1 | 16.8 million | 15 Jun 2012 |
| ZPT Vigantice | 1 | 16.8 million | 1 Jan 2014 |
| Erba Lachema s.r.o. | 3 | 1.1 million | 16 Feb 2022 |
| SKODA ELECTRIC a.s. | 2 | 1.1 million | 18 Aug 2013 |
| VNT electronics s.r.o. | 2 | 1.1 million | 30 Sep 2018 |
| Advanced Digital Technologies, s.r.o. | 1 | 1 million | 15 Apr 2018 |
| alt digital s.r.o. | 1 | 1 million | 27 Sep 2024 |
| ASES GROUP, s.r.o. | 1 | 1 million | 17 Nov 2023 |
| Avast Software s.r.o. | 1 | 1 million | 26 Jan 2019 |
| BMR s.r.o. | 1 | 1 million | 29 Oct 2022 |
| Callidus trading, spol. s r.o. | 1 | 1 million | 9 Nov 2022 |
| Cleartex s.r.o. | 1 | 1 million | 13 Nov 2022 |
| COMET SYSTEM, s.r.o. | 1 | 1 million | 10 Apr 2024 |
| CUTTER Systems spol. s r.o. | 1 | 1 million | 4 Jun 2017 |
| DevCom spol. s r.o. | 1 | 1 million | 4 Dec 2019 |
| Dueton Systems s.r.o. | 1 | 1 million | 16 Oct 2015 |
| EGMedical, s.r.o. | 1 | 1 million | 25 Jun 2021 |
| ELKO EP, s.r.o. | 1 | 1 million | 16 Oct 2015 |
| Estelar s.r.o | 1 | 1 million | 15 Jan 2022 |
| HARDWARIO a.s. | 1 | 1 million | 17 Nov 2025 |
| Hash Mining s.r.o. | 1 | 1 million | 27 May 2023 |
| Honeywell spol. s.r.o. HTS CZ o.z. | 1 | 1 million | 3 Dec 2017 |
| Imageo s.r.o. | 1 | 1 million | 8 Jul 2018 |
| INTRIPLE, a.s. | 1 | 1 million | 10 Aug 2019 |
| Invasys | 1 | 1 million | 22 Apr 2018 |
| MACH SYSTEMS s.r.o. | 1 | 1 million | 24 Apr 2022 |
| Meatest sro | 1 | 1 million | 6 Aug 2017 |
| MESIT asd, s.r.o. | 1 | 1 million | 9 Oct 2019 |
| MSV elektronika s.r.o. | 1 | 1 million | 22 Jul 2021 |
| NetX Networks a.s. | 1 | 1 million | 15 May 2021 |
| Partizan Security s.r.o. | 1 | 1 million | 28 Nov 2023 |
| Princip a.s. | 1 | 1 million | 16 Oct 2015 |
| Protronix s.r.o. | 1 | 1 million | 13 May 2021 |
| RCE systems s.r.o. | 1 | 1 million | 5 Feb 2022 |
| Simpleway Europe a.s. | 1 | 1 million | 25 Feb 2023 |
| Spedos ADS a.s. | 1 | 1 million | 19 Aug 2020 |
| Tokoz a.s. | 1 | 1 million | 24 Nov 2022 |
| Unipi Technology s.r.o. | 1 | 1 million | 16 Jan 2021 |
| Cominfo, Inc. | 8 | 32.8 thousand | 30 Jul 2008 |
| Terratel Technology s.r.o. | 3 | 12.3 thousand | 12 Feb 2012 |
| CUE, a.s. | 2 | 8.2 thousand | 30 Jul 2008 |
| EFG CZ spol. s r.o. | 2 | 8.2 thousand | 30 Jul 2008 |
| Tech Fass s.r.o. | 2 | 8.2 thousand | 30 Jul 2008 |
| TTC TELEKOMUNIKACE, s.r.o. | 2 | 8.2 thousand | 16 Oct 2016 |
| 4Jtech s.r.o. | 1 | 4.1 thousand | 12 Oct 2018 |
| Abbas, a.s. | 1 | 4.1 thousand | 22 Oct 2017 |
| AC SYSTEMS, s.r.o. | 1 | 4.1 thousand | 30 Jul 2008 |
| ACRIOS Systems s.r.o. | 1 | 4.1 thousand | 20 Oct 2020 |
| Altron, a.s. | 1 | 4.1 thousand | 30 Oct 2016 |
| ALVAT s.r.o. | 1 | 4.1 thousand | 12 Feb 2020 |
| ATAL s.r.o. | 1 | 4.1 thousand | 27 Feb 2026 |
| ATIS group s.r.o. | 1 | 4.1 thousand | 30 Jul 2008 |
| AZD Praha s.r.o. | 1 | 4.1 thousand | 30 Jul 2008 |
| AZD Praha s.r.o., ZOZ Olomouc | 1 | 4.1 thousand | 17 Feb 2022 |
| B:TECH, a. s. | 1 | 4.1 thousand | 27 Nov 2011 |
| BARCO, s.r.o. | 1 | 4.1 thousand | 23 May 2019 |
| BMR | 1 | 4.1 thousand | 25 Dec 2011 |
| CAMEA, spol. s r.o. | 1 | 4.1 thousand | 31 Mar 2013 |
| Codasip s.r.o. | 1 | 4.1 thousand | 3 Jul 2025 |
| CONTES, spol. s r.o. | 1 | 4.1 thousand | 20 Nov 2019 |
| CS-Tech s.r.o. | 1 | 4.1 thousand | 3 Jul 2025 |
| Deymed Diagnostic | 1 | 4.1 thousand | 4 May 2014 |
| DISK Multimedia s.r.o. | 1 | 4.1 thousand | 16 Nov 2014 |
| EAX Labs s.r.o. | 1 | 4.1 thousand | 25 Apr 2019 |
| Eltvor Instruments | 1 | 4.1 thousand | 12 Jan 2026 |
| ENIKA.CZ | 1 | 4.1 thousand | 7 Aug 2011 |
| Epigon spol. s r.o. | 1 | 4.1 thousand | 8 Mar 2024 |
| ERA a.s. | 1 | 4.1 thousand | 17 Dec 2017 |
| EVPU Defence a.s. | 1 | 4.1 thousand | 24 Nov 2020 |
| Foxconn 4Tech | 1 | 4.1 thousand | 18 Mar 2018 |
| GREEN Center s.r.o. | 1 | 4.1 thousand | 11 Oct 2009 |
| ID-KARTA s.r.o. | 1 | 4.1 thousand | 30 Jul 2008 |
| Inspinia Technology s.r.o. | 1 | 4.1 thousand | 6 Jun 2025 |
| JanasCard | 1 | 4.1 thousand | 13 Sep 2009 |
| JSE s.r.o. | 1 | 4.1 thousand | 22 Jun 2023 |
| KPE spol. s r.o. | 1 | 4.1 thousand | 30 Jul 2008 |
| Kramara s.r.o. | 1 | 4.1 thousand | 12 Jul 2009 |
| Lightdrop | 1 | 4.1 thousand | 7 Sep 2018 |
| Loma Systems s.r.o. | 1 | 4.1 thousand | 8 Sep 2019 |
| Lubino s.r.o. | 1 | 4.1 thousand | 10 Nov 2013 |
| Merz s.r.o. | 1 | 4.1 thousand | 13 Mar 2016 |
| Military Research Institute | 1 | 4.1 thousand | 26 Apr 2020 |
| MITE Hradec Kralove, s.r.o. | 1 | 4.1 thousand | 30 Jul 2008 |
| Moravian Instruments | 1 | 4.1 thousand | 20 Jun 2010 |
| NeurIT s.r.o. | 1 | 4.1 thousand | 1 Jul 2019 |
| POLAK CZ s.r.o. | 1 | 4.1 thousand | 25 Feb 2025 |
| Porsche engineering | 1 | 4.1 thousand | 5 Oct 2021 |
| RCD Radiokomunikace | 1 | 4.1 thousand | 27 May 2018 |
| Redcap Solutions s.r.o. | 1 | 4.1 thousand | 4 Feb 2018 |
| Ronyo Technologies s.r.o. | 1 | 4.1 thousand | 23 Aug 2009 |
| Sator Controls s.r.o. | 1 | 4.1 thousand | 21 Feb 2016 |
| Seznam.cz, a.s., CZ26168685 | 1 | 4.1 thousand | 19 Mar 2020 |
| Summit Developmen | 1 | 4.1 thousand | 30 Jul 2008 |
| Tap Home, s.r.o. | 1 | 4.1 thousand | 30 Oct 2018 |
| Tele Data Control | 1 | 4.1 thousand | 20 Feb 2011 |
| TESCAN Brno, s.r.o. | 1 | 4.1 thousand | 12 Feb 2021 |
| TESCAN GROUP, a.s. | 1 | 4.1 thousand | 29 Jun 2026 |
| TESCAN, s.r.o. | 1 | 4.1 thousand | 30 Jul 2008 |
| TESLA, a.s. | 1 | 4.1 thousand | 30 Jul 2008 |
| Trakce a.s. | 1 | 4.1 thousand | 30 Jul 2008 |
| TRIUMPH BOARD a.s. | 1 | 4.1 thousand | 10 May 2015 |
| Tronic Control ltd. | 1 | 4.1 thousand | 16 Dec 2012 |
| TTC TELEKOMUNIKACE Ltd | 1 | 4.1 thousand | 30 Jul 2008 |
| Vojensky Technicky Ustav, s.p. | 1 | 4.1 thousand | 18 Feb 2026 |
| Vytahy-Vymyslicky s.r.o. | 1 | 4.1 thousand | 31 Mar 2022 |
| WM Design s.r.o | 1 | 4.1 thousand | 13 Nov 2016 |
| ZELPOS | 1 | 4.1 thousand | 30 Jul 2008 |
Every organization with blocks registered in Czechia, sorted by total address space.