It's a user-friendly frontend to play NFS Underground on a game server: just select one, start the game, and go play online. There are also some useful features built-in: check ping and firewall rules, manage bookmarks, enable ghost mode, and links to more information regarding multiplayer. It can record lap times in Free Run mode + submit the results to the website NFS.onl which offers leaderboards, for Hot Laps and more...

Changelog:

v2.5
Lap records are now saved separately based on controller type locally and will also be saved when uploaded to the NFS.onl online database. Additionally, the input overlay now offers a digital display for older digital gamepads with analog output (axes). As always, this update includes various bug fixes and minor improvements.
NFSU Collision Disabler and Online menus Adjustments developed by Ultra Jericho is now included and used, which offers an in-game collision toggle and further improvements for multiplayer games. More info under http://nfsa.ca/f8952

v2.4
Optional input overlay with customizable color theme, optional for Free Run only, or for everything. Optimized dx9 overlay code, finally works on weak PCs + fix for missing black bars. New options for top 5 display: car-specific or overall + ladder, showing your range. Additional info display on server login and quick race menu, showing whether collisions are turned on, or in ghost mode. Displayed lap record can be personal or global, car-specific or overall. Under settings > main configuration: UDP port test, to check if you can host a game. Under settings > track records > update profile: your YouTube and Twitch channel can be added. A lot of bugfixes.

v2.3
Cars geometry check, the cars must be original, you can use the new smol model fix for 206 and Lancer though, no other modifications for cars are allowed. No new features, but several bugfixes.

v2.2
Complete overhaul of DX9 overlay: now featuring the Top 5 from NFS.onl as an optional HUD element as well as FPS informations and it's even possible to take over the original Lap Info. Also personal data will get synchronized with the online database automatically and in real time. The actual FPS and the FPSLimit will be measured and checked as well which comes with new setting rules for the online rankings: 60, 70, 85, 105 and 144 FPS are allowed, as long as the game runs stable on the framerate limit.

v2.1
New DirectX9 overlay and bugfixes

v2.0
Finally, you can upload your Free Run records, even automatically, results will appear directly on https://nfs.onl/. On a new or 2nd PC you can also import your data from the online database. The button to import/upload has been added to "My Free Run records", also new options can be found on the "Track records" tab in the settings. +Bugfixes +New savegames

v1.9
Starting from this version, Free Run records are now eligible for online rankings, as long as game speed and timings won't provide an unfair advantage, which will be checked. For more details and instructions, please refer to the information available by pressing the F1 key. Additionally, bug fixes as usual, including compatibility with the new Widescreen Fix which can be updated by first "Delete" then "Install" under Settings.

v1.8
Huge upgrade: Lap Recorder with overlay! Make sure that collisions are enabled and give your best in Free Run mode. kickStart will track your best lap times. You can review your session in the overview table under "My Free Run records". Press the F1 key for more information. Not working on XP yet. Also: bugfixes, as usual.

Please note: Recorder is now in a public testing phase, all records done with this version are not yet eligible for the upcoming online rankings.

v1.7
Instead of a message about already running, it will just bring the main window in front. Play time is shown when game is started and notifications will reactivate after session is over. Starting game by holding Shift will keep notifications activated (for offline session). Start button will bring the game to front if it's already running, to avoid multiple instances. Hotkey AltGr+K (only if close to tray is enabled) will make mouse pointer visible which makes it a very good alternative to Alt+Tab. Making screenshots with F10 now has accustical feedback. Users online on favorite servers do now have a timeout of 5 minutes, so that players in a race won't disappear all of a sudden. Also, lots of bugs have been fixed and a few minor cosmetics have been done.

v1.6
Additional files are now outsourced to subfolder "files". Server Changer script mod is now default to configure the game server via INI file. In-game music playlist can also be edited. There is a GUI to remove, install, and configure ASI plugins like Widescreen Fix. New options are available to start minimized, startup with Windows, close to the tray, and add a shortcut to the desktop. Custom servers can be favorited for monitoring. Get notified about online users on favorites with visual and acoustic signals, and use custom MP3 files. New user game files management: easily import 100% savegames. Create a new profile for that and even change TJ's unique upgrades for the underground car on the fly. New hotkeys are available: take screenshots with F10, access more info with F1. There are also some new graphics and a new theme.

v1.5
Widescreen Fix is now integrated, allowing installation and configuration via a graphical interface.

The official server was shut down by EA back in 2006. However, it's possible to play online again as there is server software available that emulates the official one: https://github.com/HarpyWar/nfsuserver

kickStart, the netplay launcher, is preparing a list of such servers and also checks if they are online. You can simply create an account on each server, just use a fake email for that, it doesn't matter at all.