Maximize XP in Payday 2 - Top Tips for Leveling Up Fast

Complete Challenges like Career, Combat, and Heist to gain Infamy Points and XP. Prioritize Combat and Heist ones.
Max level is 150 but all skills and weapons unlock by level 100. Last 50 levels are for flexing expertise.
Good XP farm heists are Dirty Ice, Road Rage, No Rest for the Wicked, Rock the Cradle, and 99 Boxes.
Stealth heists give weapon XP but loud is better for quick XP. Don't force stealth just for XP.
If you complete Challenges but get 0 XP, it's likely a bug. Restarting the game should fix it.

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Relevant topic timeline:

9/7/2023

Payday 3 preview: Starbreeze sets up the next decade of Payday - Dexerto

Payday 3, the long-awaited successor to Payday 2, offers a promising gameplay experience with a balance between accessibility for newcomers and challenges for returning players, as well as a wide range of options for loadouts and customization.

9/21/2023

Payday 3 Offers Streamlined Heists and Improved Stealth for New and Veteran Players Alike

Payday 3 offers a streamlined and accessible entry point for newcomers while still maintaining the familiar heisting fun that veterans of the series will appreciate.

9/22/2023

Review: Payday 3's dated design and technical issues make it a repetitive grind

Payday 3, the cooperative heist FPS sequel, offers improved stealth mechanics and new game engine, but is hindered by a lack of content, outdated gameplay, underwhelming AI, and unfinished cutscenes.

9/22/2023

Payday 3 Launch Plagued by Technical Issues and Poor Reviews

Payday 3 has experienced a rocky launch, with players reporting issues such as lengthy set-up processes, slow matchmaking, and a poor user experience, leading to a low score on PC and negative feedback from fans.