Debug screen



The debug screen is triggered when the key is pressed (+ on Macs [by default; the behaviour of the F keys can be changed in Keyboard preferences] and some laptops). It shows the chunk cache, the memory usage, the map seed, 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. Pressing + (++ on Mac and some laptops) brings up the debug screen but without the graphs, as of 1.2.4.

Rendering graph
The graph at the bottom screen displays rendering performance information. The height of each bar indicates the time taken to render each frame.

Green bars represent a frame rate higher than or equal to 60 frames per second, and red for less than 60. Once the graph has moved all the way to the right of the graph area, it will return to the left and begin to overwrite older bars.

The speed at which the graph writes new bars is dependent on the current frame rate, as one bar is written per frame.

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.

History


In Indev, Infdev, and early Alpha versions, the debug screen only had what we recognize as "the top part with all the numbers". This debug screen was not activated with F3, but as a toggle in the options. In Alpha 1.1.0, the debug screen was no longer listed as an option and required F3 to be held down to activate. In Alpha 1.2.3, the coordinates were added.

In Beta 1.3, the debug screen, along with other F# controls, became a toggle. Also, between Beta 1.3 and Beta 1.7, when you activated the debug screen, it would show numbers above every mob; these numbers being the mob's Entity ID. These were visible through blocks, making F3 a very useful mob-finder. Some considered this cheating and felt that it took away from the game. Because of this, the Entity ID label was removed in Beta 1.8.

In Beta 1.7, the "f" coordinate was made visible in the debug screen (facing direction).

In Beta 1.8, the ability to see the level's seed was added.

In 1.2, information about the biome and light level of the player's location were added. The seed in multiplayer was made hidden, showing as "0" prior to 1.2.5.

In the 12w18a snapshot, information about the player's speed and whether the player is touching the ground were added. Information about the world's seed was also removed.

Trivia

 * Lc, Biome, and the lighting values do not display when you are in the void or above y = 256 (in the Overworld)


 * When triggered in the nether, the "B" (biome) displays the biome of "Hell". In The End, it will indicate the biome "Sky", likely because The End was originally going to be the Sky Dimension.


 * The coordinates are useful to return to a past location where the player has found rare ores.

Bugs

 * At very low frame rates the graph can rise high enough so that it will cover values like the coordinates. This can be fixed by activating the debug screen by shift+F3, which will not render the graphs.