The Minecraft wiki claims that chunk load distance in multiplayer is a radius of 10 chunks centred on the player. I ran a test server and confirmed this by walking about 160 metres away from a ring oscillator and watching its output stop exactly when expected. I then tried playing exactly the same world but with Forge added to the server JAR (and, obviously, the client). The clock kept running! Chunk load distance with Forge installed seems to be more like 320 metres instead of 160, or 20 chunks instead of 10. Does anyone else see this happening? Is this intended behaviour I can rely on when building, or is it a bug that's likely to be fixed in future versions of Forge?

We do not touch anything related to the distance of loaded chunks. We do provide hooks for modders to be able to prevent the unloading of chunks.

However, as I said, none of the actual numbers are changed so there shouldn't be any reason that they are loaded extraneously.

Perhaps you're running into the spawn chunks, which are not unloaded, ever.

I was about a kilometre from the spawn point. I didn't have any relevant mods installed; I literally swapped out a vanilla minecraft_server.jar (which dropped chunks at 160 metres) for one with Forge in it (which dropped chunks at the longer distance) and nothing else.

Oh well, I guess I'll just build my system assuming this is a feature and not a bug; if it ever breaks, I'll either rebuild it or increase the server's view distance.

I just had Matabase confirm that the chunks loaded in a 5 chunk radius for him.

Perhaps you are using Optifine, or some other mod that increases your render distance, chunks will not be unloaded if they are requested by the user's render distance.

I am not using Optifine. My client JAR has only ML and Forge. My server JAR has only Forge. I had some mods installed in my client's mods/ directory when I tried this test, but none in the server's.