Barrier

A barrier is a transparent solid block used to create impenetrable boundaries.

Obtaining
Like command blocks, jigsaw blocks and structure blocks, barriers can only be obtained using commands such as, are not available in the creative inventory, and cannot be broken in vanilla survival mode.

Usage
Barrier blocks are mainly used to build an impenetrable barrier that cannot be broken in standard survival mode play. For example, they can be used to protect a reserved area from entry by players, mobs, and other entities. Unlike other kinds of unbreakable blocks that could be used for this purpose (such as bedrock), barrier blocks are unobtrusive because they are invisible.

In the player's inventory, the block is displayed as a red box with a slash through it, but when placed it is completely invisible.

Barriers are transparent to light and do not block a beacon. Fences, iron bars, glass panes and similar blocks will not visually connect with barriers. Barriers interact with blocks and mobs as a solid block. All dependent blocks can be placed on a barrier, such as torches or redstone, and it will suffocate mobs. Mobs cannot spawn on barriers. The red cross texture, however, will be revealed as particle effects when falling or sprinting on them, regardless of what gamemode the player is in.

In creative mode, if a player is holding a barrier block in their hand, all placed barrier blocks display the barrier icon as a particle. This effect is client-side, and if a player holds a barrier block in survival, the particle won't display. Barrier blocks will not be shown if the particle setting is set to "minimal". Barriers cannot be pushed by pistons. They, furthermore, have a greater amount of blast resistance than any other unbreakable block.

Barrier blocks can be waterlogged by being placed into water source blocks. See Waterlogging for more details on what blocks can be waterlogged.

Trivia

 * The symbol used is not compliant with ISO 3864-1, as the diagonal line is mirrored.
 * Invisible bedrock, a technical block in Bedrock Edition and New Nintendo 3DS Edition, shares many features with the barrier block.
 * The barrier block is in the Legacy Console Edition of the game, but requires an inventory editor/external tool.
 * This block has a higher blast resistance than any other unbreakable block in the game.
 * In Minecraft 4k, there is barrier on the bottom of the map, which is unbreakable by any means.
 * The barrier's blockstate file in the game's assets is functionally identical to most standard blocks in the game, using a single, unnamed variant which uses  as a model.
 * The barrier's vanilla block model only defines what texture to use for block breaking particles, and doesn't have a parent model or anything that would give the block a physical shape.
 * However, using a custom resource pack that modifies the barrier block model to use the  parent model (which is used by most simple blocks with only one texture) with the barrier item's texture as the block's texture will still not allow barriers to render.