client.json

client.json is the file that accompanies client.jar in .minecraft/versions/<version> and lists the version's attributes. When using the latest version of the Minecraft Launcher, it is named <game version>.json. The JSON file for specific versions is located in the version_manifest.json file.

JSON format

This is the JSON format for client.json.

• [NBT Compound / JSON Object] The root tag.
  • [NBT Compound / JSON Object] arguments:
    • [NBT List / JSON Array] game: Contains arguments supplied to the game, such as information about the username and the version.
      • [String] An argument.
      • [NBT Compound / JSON Object] A conditional argument.
        • [NBT List / JSON Array] rules: A list of rules.
          • [NBT Compound / JSON Object] A rule.
            • [String] action: One of "allow" or "disallow".
            • [NBT Compound / JSON Object] features: Includes a set of features that can be checked.
              • [Boolean] is_demo_user: Appears only in the first appearance of the compound tag.
              • [Boolean] has_custom_resolution: Appears only in the second appearance of the compound tag.
              • [Boolean] has_quick_plays_support: Appears only in the third appearance of the compound tag.
              • [Boolean] is_quick_play_singleplayer: Appears only in the fourth appearance of the compound tag.
              • [Boolean] is_quick_play_multiplayer: Appears only in the fifth appearance of the compound tag.
              • [Boolean] is_quick_play_realms: Appears only in the sixth appearance of the compound tag.
        • [String][NBT List / JSON Array] value: An argument or a list of arguments that is added when the condition is matched.
    • [NBT List / JSON Array] jvm: Contains JVM arguments, such as information about memory allocation, garbage collector selection, or environment variables.
      • [NBT Compound / JSON Object]: A conditional argument.
        • [NBT List / JSON Array] rules: A list of rules.
          • [NBT Compound / JSON Object]: A rule.
            • [String] action: One of "allow" or "disallow".
            • [NBT Compound / JSON Object] features: The launcher can detect this, but it's currently unused.
            • [NBT Compound / JSON Object] os:
              • [String] name: One of "windows", "osx" or "linux".
              • [String] version: Contains a regex intended to be checked against System.getProperty("os.version").
              • [String] arch: Appears only in the fourth appearance of the compound tag. Its value is "x86".
        • [String][NBT List / JSON Array] value: An argument or a list of arguments that is added when the condition is matched.
  • [NBT Compound / JSON Object] assetIndex:
    • [String] id: The assets version.
    • [String] sha1: The SHA1 hash of the assets file.
    • [Int] size: The size of the version.
    • [Int] totalSize: The total size of the version.
    • [String] url: The URL that the game should visit to download the assets.
  • [String] assets: The assets version.
  • [Int] complianceLevel: 0 until 1.16.4-pre2, and 1 for all versions after. A value of 0 causes the official launcher to warn the player about missing player safety features when this version is selected.
  • [NBT Compound / JSON Object] downloads:
    • [NBT Compound / JSON Object] client: The client.jar download information.
      • [String] sha1: The SHA1 hash of the jar.
      • [Int] size: The size of the jar in bytes.
      • [String] url: The URL the launcher should visit to download the file.
    • [NBT Compound / JSON Object] client_mappings: The obfuscation maps for this client version. Added in Java Edition 19w36a but got included in 1.14.4 also. Repeats the structure of the client download information.
    • [NBT Compound / JSON Object] server: The server download information. Repeats the structure of the client download information.
    • [NBT Compound / JSON Object] server_mappings: The obfuscation maps for this server version. Added in Java Edition 19w36a but got included in 1.14.4 also. Repeats the structure of the client download information.
    • [NBT Compound / JSON Object] windows_server: The Windows server download information. Removed in Java Edition 16w05a, but is still present in prior versions. Repeats the structure of the client download information.
  • [String] id: The name of this version client (e.g. 1.14.4).
  • [NBT Compound / JSON Object] javaVersion: The version of the Java Runtime Environment to use.
    • [String] component: Its value is "jre-legacy" until 21w18a, "java-runtime-alpha" until 1.18-pre1, "java-runtime-beta" until 22w17a, "java-runtime-gamma" until 24w13a, and "java-runtime-delta" since 24w14a.
    • [Int] majorVersion: Its value is 8 until 21w18a, 16 until 1.18-pre1, 17 until 24w13a, and 21 since 24w14a.
  • [NBT List / JSON Array] libraries: A list of libraries.
    • [NBT Compound / JSON Object]: A library.
      • [NBT Compound / JSON Object] downloads: The library's download information.
        • [NBT Compound / JSON Object] artifact: Info about the artifact.
          • [String] path: Path to store the downloaded artifact, relative to the "libraries" directory in .minecraft.
          • [String] sha1: The SHA1 hash of the file.
          • [Int] size: The size of the file in bytes.
          • [String] url: The URL that the game should visit to download the file.
        • [NBT Compound / JSON Object] classifiers: Appears only for some libraries.
          • [NBT Compound / JSON Object] <classifier>: Specifies the artifact information for the artifact with this specific classifier. Repeats the artifact structure above.
      • [String] name: A maven name for the library, in the form of "groupId:artifactId:version".
      • [String] url: The URL of the Maven repository (used by Forge).
      • [NBT Compound / JSON Object] natives: Information about native libraries (in C) bundled with this library. Appears only when there are classifiers for natives.
        • [String]: This tag's name depends on the natives that appear in the classifiers, it will be one of "windows", "osx" or "linux".
      • [NBT Compound / JSON Object] extract: Rules to follow when extracting natives from a library.
        • [NBT List / JSON Array] exclude: Paths to exclude.
          • [String]: Its value is "META-INF/".
      • [NBT List / JSON Array] rules: Contains a compound with the tags "action" and "os", as shown above.
  • [NBT Compound / JSON Object] logging: Information about Log4j log configuration.
    • [NBT Compound / JSON Object] client:
      • [String] argument: The JVM argument for adding the log configuration. Its value is "-Dlog4j.configurationFile=${path}".
      • [NBT Compound / JSON Object] file: The Log4j2 XML configuration used by this version for the launcher for launcher's log screen.
        • [String] id: Its value is "client-1.12.xml", but may differ for older versions.
        • [String] sha1: The SHA1 hash for this file.
        • [Int] size: The size of this file in bytes.
        • [String] url: The URL the launcher should visit to download the file.
      • [String] type: Its value is "log4j2-xml".
  • [String] mainClass: The main game class; for modern versions, it is net.minecraft.client.main.Main, but it may differ for older or ancient versions.
  • [Int] minimumLauncherVersion: The minimum Launcher version that can run this version of the game.
  • [String] releaseTime: The release date-time in ISO-8601 extended offset format.
  • [String] time: Same as "releaseTime".
  • [String] type: The type of this game version. One of "release", "snapshot", "old_beta" or "old_alpha"

History

Java Edition
1.6.1			13w16a				With the new launcher, versions are now stored in .minecraft/versions and each version has its own folder with a minecraft.jar (which is now called client.jar) and a .json file, which is the client.json.
1.7.2			13w39a				Added the [NBT Compound / JSON Object] logging tag in the root tag.
1.9			16w05a				Removed the [NBT Compound / JSON Object] windows_server tag, however, it remains present for versions that already have it.
1.13			17w43a				The [NBT Compound / JSON Object] arguments tag replaced the old [String] minecraftArguments tag.
1.15			19w36a				Obfuscation mappings are now listed in the [NBT Compound / JSON Object] downloads tag. They are implemented in 1.14.4 also.
1.16			20w21a				Added two new arguments: disableChat, which disables the chat in-game, and disableMultiplayer, which disables the "Multiplayer" and "Minecraft Realms" buttons.
1.17			20w45a				Added the [NBT Compound / JSON Object] javaVersion tag with all its children.
1.20			23w14a				In [NBT List / JSON Array] game, added [Boolean] has_quick_plays_support, [Boolean] is_quick_play_singleplayer, [Boolean] is_quick_play_multiplayer, and [Boolean] is_quick_play_realms to [NBT List / JSON Array] rules.