| SC 13G/A | 2019-01-24 | BlackRock Inc. | COGENT COMMUNICATIONS HOLDINGS, INC. | 6,865,395 | 14.8% | EDGAR |
| SC 13G/A | 2018-03-12 | VANGUARD GROUP INC | COGENT COMMUNICATIONS HOLDINGS, INC. | 4,601,795 | 10.0% | EDGAR |
| SC 13G | 2018-02-14 | RENAISSANCE TECHNOLOGIES LLC | COGENT COMMUNICATIONS HOLDINGS, INC. | 2,775,300 | 6.0% | EDGAR |
| SC 13G/A | 2018-02-13 | FMR LLC | COGENT COMMUNICATIONS HOLDINGS, INC. | 2,058,292 | 4.5% | EDGAR |
| SC 13G/A | 2018-02-09 | VANGUARD GROUP INC | COGENT COMMUNICATIONS HOLDINGS, INC. | 4,566,346 | 9.9% | EDGAR |
| SC 13G/A | 2018-02-07 | FRONTIER CAPITAL MANAGEMENT CO LLC | COGENT COMMUNICATIONS HOLDINGS, INC. | 1,256,479 | 2.7% | EDGAR |
| SC 13G/A | 2018-01-19 | BlackRock Inc. | COGENT COMMUNICATIONS HOLDINGS, INC. | 6,288,095 | 13.7% | EDGAR |
| SC 13G/A | 2017-02-14 | FMR LLC | COGENT COMMUNICATIONS HOLDINGS, INC. | 2,945,278 | 6.5% | EDGAR |
| SC 13G/A | 2017-02-10 | VANGUARD GROUP INC | COGENT COMMUNICATIONS HOLDINGS, INC. | 4,697,638 | 10.3% | EDGAR |
| SC 13G/A | 2017-02-10 | FRONTIER CAPITAL MANAGEMENT CO LLC | COGENT COMMUNICATIONS HOLDINGS, INC. | 2,855,908 | 6.3% | EDGAR |
| SC 13G/A | 2017-01-12 | BlackRock Inc. | COGENT COMMUNICATIONS HOLDINGS, INC. | 4,703,620 | 10.3% | EDGAR |
| SC 13G/A | 2016-08-10 | VANGUARD GROUP INC | COGENT COMMUNICATIONS HOLDINGS, INC. | 4,708,349 | 10.3% | EDGAR |
| SC 13G/A | 2016-05-10 | BlackRock Inc. | COGENT COMMUNICATIONS HOLDINGS, INC. | 4,536,654 | 10.0% | EDGAR |
| SC 13G/A | 2016-02-12 | FMR LLC | COGENT COMMUNICATIONS HOLDINGS, INC. | 5,070,064 | 11.2% | EDGAR |
| SC 13G/A | 2016-02-12 | FRONTIER CAPITAL MANAGEMENT CO LLC | COGENT COMMUNICATIONS HOLDINGS, INC. | 3,914,620 | 8.6% | EDGAR |
| SC 13G/A | 2016-02-11 | VANGUARD GROUP INC | COGENT COMMUNICATIONS HOLDINGS, INC. | 3,479,377 | 7.7% | EDGAR |
| SC 13G/A | 2016-01-26 | BlackRock Inc. | COGENT COMMUNICATIONS HOLDINGS, INC. | 3,068,965 | 6.8% | EDGAR |
| SC 13G/A | 2015-10-05 | COLUMBIA WANGER ASSET MANAGEMENT LLC | COGENT COMMUNICATIONS HOLDINGS, INC. | 10 | - | EDGAR |
| SC 13G/A | 2015-07-10 | FMR LLC | COGENT COMMUNICATIONS HOLDINGS, INC. | 4,846,105 | 10.5% | EDGAR |
| SC 13G/A | 2015-02-13 | FRONTIER CAPITAL MANAGEMENT CO LLC | COGENT COMMUNICATIONS HOLDINGS, INC. | 4,570,012 | 9.9% | EDGAR |