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Level encoding/decoding ​

Despite Geometry Dash levels being stored in a plaintext, human-readable format, the game will resort to storing level data in a compressed binary format when storing them in the game's memory or files(albeit for compatibility reasons levels can also be loaded directly in a uncompressed format).

Official levels are stored in <game installation folder>\Resources\LevelData.plist (filename depends on game, LevelDataSubzero.plist for Geometry Dash Subzero, etc.)

Compressed levels are actually composed out of two things: Base64 encoding and ZLIB compression.

Encoding ​

To encode a level you take first the level string and compress() it, afterwards you need to encode the resulting byte sequence with Base64 encoding.

If you are encoding an official level and want to put it in LevelData.plist, you need to remove the first 13 characters in the beginning of the base64 encoded string.

Python ​

py
import base64
import gzip

def encode_level(level_string: str, is_official_level: bool) -> str:
    gzipped = gzip.compress(level_string.encode())
    base64_encoded = base64.urlsafe_b64encode(gzipped)
    if is_official_level:
        base64_encoded = base64_encoded[13:]
    return base64_encoded.decode()

Decoding ​

To decompress the level you'll first need to decode the compressed string in it's B64 encoded form, then you need to decompress() the resulting bytes to obtain a valid level string which can be read by the game.

If you are decoding an official level, you need to add H4sIAAAAAAAAA at the beginning of the compressed string.

Python ​

py
import base64
import zlib


def decode_level(level_data: str, is_official_level: bool) -> str:
    if is_official_level:
        level_data = 'H4sIAAAAAAAAA' + level_data
    base64_decoded = base64.urlsafe_b64decode(level_data.encode())
    # window_bits = 15 | 32 will autodetect gzip or not
    decompressed = zlib.decompress(base64_decoded, 15 | 32)
    return decompressed.decode()