Debug screen



The debug screen is triggered when the key is pressed ( on some laptops [by default; the behavior of the F keys can be changed in Keyboard preferences]). It shows the chunk cache, the memory usage, various parameters, the player's map coordinates and a graph that measures the game's current frame rate. It can be very useful for telling other players your map location and monitoring performance.

Legend
When displaying reduced debug info, only the starred items are included.

Profiler graph
Pie charts in the lower right of the debug screen display real time profiling information. More detailed information about one section can be displayed by using the keys 1-9. Press 0 to go back to the previous section.

Frame rate
The frame rate (also known as frame frequency) is the frequency rate at which a video device produces unique consecutive images called frames. Frames are still pictures that when sequence together form a fluid animation that is the basis for all moving media. Frame rate is most often expressed in frames per second (FPS). The frame rate can be viewed under the version number.

Frame time graph
Bar chart in the lower left of the Alt+F3 debug screen displays real time measurement of seconds per frame with lines marking 1/60s and 1/30s per frame. The graph is color coded from green to yellow to red, with green being faster frame time, red being slower frame time, and yellow in between.

More debug-keys

 * : Reload all chunks
 * : Toggle visibility of hitboxes of entities. It also shows which direction entities are looking in using a blue line
 * : Make a debug crash (press keys for 10 seconds)
 * : Clear chat history (including previously typed messages and commands)
 * : Toggle IDs of items, the durability of tools, the armor color and the scale of maps
 * : Toggle automatic pause when Minecraft loses focus on / off
 * : Reload textures and models
 * : Reload the sound engine and all resources
 * : Shows root

Trivia

 * Lc, Biome, and the lighting values do not display when you are in the void or above y = 255 (in the Overworld)
 * When triggered in the Nether, the "B" (biome) displays the biome of "Hell". In the End, until release 1.8 (snapshot 14w17a) it indicated the biome "Sky", likely because The End was originally going to be the Sky Dimension.
 * When used in a chunk that was created prior to Alpha 1.2 (when there were no biomes), the B field will read "Ocean".
 * Deeper into the profiler, some tasks will have numbers higher than 9 and can't be accessed. Pressing the two keys simultaneously will not open the task.