Why is uplink slower than downlink?

For many users, uploading files is quite a bit slower than downloading files. This is usually normal, because most high-speed Internet connections, including cable modems and DSL, are asymmetric — they are designed to provide much better speed for downloading than uploading. Since most users spend much more time downloading (which includes viewing web pages or multimedia files) than they do uploading, high speed Internet providers have designed their systems to give priority to downloading. So if your upload speed appears to be slower than your download speed, this is probably expected.