| Apr 26, 2026 | Heidarsson | 0–1 | Ernisson | Boðsmót TR 2026 - B flokkur | East Indian Defense | |
| Apr 25, 2026 | Sigurdarson | 0–1 | Heidarsson | Boðsmót TR 2026 - B flokkur | English Opening: Symmetrical Variation, Ultra-Symmetrical Variation | |
| Apr 25, 2026 | Heidarsson | 1–0 | Hermannsson | Boðsmót TR 2026 - B flokkur | King's Indian Attack, with e6 | |
| Apr 24, 2026 | Skarphedinsson | 1–0 | Heidarsson | Boðsmót TR 2026 - B flokkur | Catalan Opening | |
| Apr 24, 2026 | Heidarsson | ½–½ | Davidsson | Boðsmót TR 2026 - B flokkur | Semi-Slav Defense: Accelerated Move Order | |
| Mar 26, 2026 | Heidarsson | 0–1 | Kurmann | Reykjavik Open 2026 | Queen's Pawn Game: London System | |
| Jun 9, 2024 | Heidarsson | 0–1 | Birkisson | Round 9: Heidarsson, Mikael Bjarki - Birkisson, Bjorn Holm | Queen's Gambit Declined | |
| Jun 7, 2024 | Heidarsson | ½–½ | Thorsteinsdottir | Round 7: Heidarsson, Mikael Bjarki - Thorsteinsdottir, Hallgerdur | English Opening: Symmetrical Variation, Three Knights Variation | |
| Jun 2, 2024 | Heidarsson | 0–1 | Ptacnikova | Round 2: Heidarsson, Mikael Bjarki - Ptacnikova, Lenka | Dutch Defense: Raphael Variation | |
| Jun 1, 2024 | Birkisson | ½–½ | Heidarsson | Round 1: Birkisson, Bardur Orn - Heidarsson, Mikael Bjarki | French Defense: Exchange Variation | |
| Nov 15, 2023 | Heidarsson | 0–1 | Villa Tornero | u14 | Benoni Defense: Taimanov Variation | |
| Nov 13, 2023 | Heidarsson | 0–1 | Goh | u14 | Queen's Gambit Declined: Exchange Variation, Positional Variation | |
| Sep 2, 2021 | Heidarsson | 1–0 | Moller | European Individual Chess Championship 2021 - Reykjavik Open | Slav Defense: Three Knights Variation | |
| Sep 1, 2021 | Hreinsson | 1–0 | Heidarsson | European Individual Chess Championship 2021 - Reykjavik Open | Indian Defense: West Indian Defense | |
| Aug 31, 2021 | Heidarsson | ½–½ | Pozimski | European Individual Chess Championship 2021 - Reykjavik Open | Queen's Gambit Accepted: Central Variation, McDonnell Defense | |
| Aug 30, 2021 | Briem | 1–0 | Heidarsson | European Individual Chess Championship 2021 - Reykjavik Open | Benoni Defense: Pawn Storm Variation | |
| Aug 29, 2021 | Heidarsson | 1–0 | Hallmundarson | European Individual Chess Championship 2021 - Reykjavik Open | Indian Defense: Anti-Nimzo-Indian | |
| Aug 28, 2021 | Haraldsson | 1–0 | Heidarsson | European Individual Chess Championship 2021 - Reykjavik Open | Benoni Defense: King's Pawn Line | |
| Aug 27, 2021 | Heidarsson | 0–1 | Player | European Individual Chess Championship 2021 - Reykjavik Open | Queen's Gambit Accepted: Central Variation, Alekhine System | |
| Aug 26, 2021 | Loiseau | 1–0 | Heidarsson | European Individual Chess Championship 2021 - Reykjavik Open | English Opening: Symmetrical Variation, Three Knights Variation | |
| — | Heidarsson | 0–1 | Normann Topp | Nordic Youth Chess Championship | Benoni Defense: Semi-Benoni | |
| — | Heidarsson | 1–0 | Magnussen | Nordic Youth Chess Championship | Catalan Opening: Closed | |
| — | Heidarsson | 0–1 | Salonen | Nordic Youth Chess Championship | Catalan Opening: Open Defense | |
| — | Religa | 1–0 | Heidarsson | Nordic Youth Chess Championship | Bird Opening: Dutch Variation | |
| — | Valpas | ½–½ | Heidarsson | Nordic Youth Chess Championship | French Defense: Advance Variation, Euwe Variation | |
| — | Davidsen | 0–1 | Heidarsson | Nordic Youth Chess Championship | French Defense: Tarrasch Variation, Closed Variation | |
