Data Transfers · Speed and advanced options
What does Streams per file do, and why is my one big file slow?
Short answer: Streams per file fetches several pieces of one large file at the same time (1–16, default 4) — the setting that speeds up a single big file. More streams help until the server or connection is the limit.
Streams per file splits one large file into pieces and fetches several pieces at the same time (1 to 16, default 4). That's what speeds up a single big file — Parallel transfers only helps when there are many files.
More streams is usually faster until the server or your connection becomes the limit; 4 is a good starting point, and going much higher rarely helps. During a large download the detail pane shows each stream, so you can tell a slow server from a stalled piece.
Related: Parallel transfers · Large downloads that resume