William Jansen
2022
| Usopenjuniorchampionships | 2R | |
| Us Open Junior | 2R | |
| Wimbledon Junior | 2R | |
| J1Roehampton | Quarter | |
| J1Nottingham | Semi | |
| J2Aldershot | [4] | Win |
| J3Loughborough-2 | [2] | Final |
| J3Loughborough | [2] | Final |
| J1Salinas | 1R | |
| J1Barranquilla | [15] | 3R |
| J1Sanjose | 1R |
2021
| J4Kranj | [2] | Quarter |
| Wimbledon Junior | 1R | |
| Thejuniorchampionships | 1R | |
| J1Roehampton | 1R | |
| J3Megrine | Quarter | |
| J5Sfax | Semi | |
| J4Sousse | 2R | |
| J5Dakar-2 | [2] | Quarter |
| J5Dakar | [2] | 2R |
| J5Nairobi | [3] | Quarter |
| J4Nairobi-2 | 1R | |
| J4Nairobi | 2R |
Nation
GBR
World Ranking
ATP Ranking　1322th
Year-end Junior World Ranking
- Year-end 2022 79th
- Year-end 2021 212th
- Year-end 2020 713th
- Year-end 2019 2108th
Match Details
2022 Usopenjuniorchampionships
| W | 1R | Jeremy Jin | 6-1 6-3 |
| L | 2R | Michael Zheng | 2-6 5-7 |
2022 Us Open Junior
| W | 1R | Jeremy Jin | 6-1 6-3 |
| L | 2R | Michael Zheng | 2-6 5-7 |
2022 Wimbledon Junior
| W | 1R | Juan Carlos Prado Angelo | 7-5 7-6 |
| L | 2R | Gilles Arnaud Bailly | 4-6 3-6 |
2022 J1Roehampton
| W | 1R | Ignacio Buse | 6-3 7-5 |
| W | 2R | Jaden Weekes | 6-2 5-7 7-6 |
| W | 3R | Michael Zheng | 6-3 6-1 |
| L | QF | Alex Michelsen | 6-3 5-7 3-6 |
2022 J1Nottingham
| W | 1R | Luka Novakovic | 3-6 7-5 6-3 |
| W | 2R | Nicholas Godsick | 7-5 6-0 |
| W | 3R | Ron Ellouck | 6-2 6-4 |
| W | QF | Gabriel Debru | 7-6 7-6 |
| L | SF | Bor Artnak | 6-7 3-6 |
2022 J2Aldershot
| W | 1R | James Beaven | 6-4 7-6 |
| W | 2R | Henry Jefferson | 7-5 6-2 |
| W | QF | Sean Daryabeigi | 6-2 6-0 |
| W | SF | Louis Bowden | 3-6 7-5 6-4 |
| W | F | Phoenix Weir | 6-2 6-3 |
2022 J3Loughborough-2
| W | 1R | Markus Molder | 6-2 6-2 |
| W | 2R | Viktor Frydrych | 6-1 6-2 |
| W | QF | Jamie Diack | 6-1 6-2 |
| W | SF | Benjamin Gusic Wan | 6-2 6-1 |
| L | F | Luca Pow | 1-6 0-6 |
2022 J3Loughborough
| W | 1R | Kacper Szymkowiak | 7-6 6-1 |
| W | 2R | Fabio Nestola | 6-1 6-1 |
| W | QF | Viktor Frydrych | 6-1 6-2 |
| W | SF | Hugo Coquelin | 6-0 6-0 |
| L | F | Luca Pow | 3-6 4-6 |
2022 J1Salinas
| L | 1R | Enrique Pena | 2-6 3-6 |
2022 J1Barranquilla
| W | 2R | Felipe Pinzon Moreno | 6-3 6-2 |
| L | 3R | Nicholas Godsick | 2-6 4-6 |
2022 J1Sanjose
| L | 1R | Preston Stearns | 2-6 1-6 |
2021 J4Kranj
| W | 2R | Ziga Svec | 6-2 6-1 |
| W | 3R | Job Japelj | 6-1 6-2 |
| L | QF | Giacomo Nosei | 4-6 6-2 3-6 |
2021 Wimbledon Junior
| L | 1R | Bruno Kuzuhara | 5-7 7-6 3-6 |
2021 Thejuniorchampionships
| L | 1R | Bruno Kuzuhara | 5-7 7-6 3-6 |
2021 J1Roehampton
| L | 1R | Aleksander Orlikowski | 1-6 6-3 3-6 |
2021 J3Megrine
| W | 1R | William Jucha | 6-3 6-0 |
| W | 2R | Yassine Dlimi | - - - |
| L | QF | Wissam Abderrahman | 4-1 1-4 2-4 |
2021 J5Sfax
| W | 1R | Rodrigo Deleu | 6-3 6-2 |
| W | 2R | Youssef Labbene | 6-2 6-2 |
| W | QF | Gabriel Berner | 6-2 6-1 |
| L | SF | Pablo Trochu | 5-7 2-6 |
2021 J4Sousse
| W | 1R | Rodrigo Deleu | 6-2 6-1 |
| L | 2R | Seydina Andre | 2-6 2-6 |
2021 J5Dakar-2
| W | 1R | John Gabelic | 6-4 6-0 |
| W | 2R | Massimo Giunta | 6-3 6-2 |
| L | QF | Maxime Dubouch | 6-3 0-6 4-6 |
2021 J5Dakar
| W | 1R | Tiago Boschmans | 6-4 6-1 |
| L | 2R | Nicolas Recoura | 4-6 0-3 |
2021 J5Nairobi
| W | 1R | Ofer Hacohen | 7-6 6-4 |
| W | 2R | Clement Bergantz | - - - |
| L | QF | Theo Herrmann | 3-6 3-6 |
2021 J4Nairobi-2
| L | 1R | Seydina Andre | 2-6 3-6 |
2021 J4Nairobi
| W | 1R | Eytan Miessen | 6-2 6-1 |
| L | 2R | Etienne Marty | 1-6 2-6 |
Junior Tennis Database is a site that summarizes the results of ITF junior tennis tournaments.
Number of registered tournaments: 9280, Number of registered players: 5,767, Number of registered results: 305,685