Old School RuneScape RuneLite "error fetching bootstrap": fix
Written by
Last checked
September 25, 2026
RuneLite will not start, and launcher.log shows "error fetching bootstrap" with an exception such as "Server returned HTTP response code: 403".
Also appears as: error fetching bootstrap, Server returned HTTP response code: 403, runelite error fetching bootstrap, runelite not launching, osrs error code 403, runelite ConnectException connection timed out
RuneLite's own troubleshooting page says "error fetching bootstrap" in launcher.log means the launcher cannot reach RuneLite's servers to get the start-up file, and the accompanying exception tells you why. A "ConnectException: Connection timed out" is caused by a firewall blocking the connection or a routing issue. A "Server returned HTTP response code: 403" means the server saw the request and is denying it, which RuneLite says is Cloudflare intentionally blocking the connection. A "SignatureException: Signature length not correct: got 0 but was expecting 512" is caused by a router or other software sitting in the middle of the connection. A separate "Error loading RS!" with "SocketTimeoutException: timeout" in client.log means the client could not fetch the game from Jagex, usually because of a slow or inconsistent connection. RuneLite is a third-party client, but Jagex lists it as approved on its recommended specifications page.
What to try
- 01Open launcher.log in your RuneLite logs folder (%userprofile%\.runelite\logs on Windows, $HOME/.runelite/logs on Linux and macOS) and find which exception follows "error fetching bootstrap".Confirmed
- 02If it says "ConnectException: Connection timed out", add a firewall exception for RuneLite (in Windows Security, Firewall and network protection, allow an app through the firewall), or reset or change your network.Confirmed
- 03If it says "Server returned HTTP response code: 403", the connection is being blocked at RuneLite's end. RuneLite's page suggests changing networks; it does not say why the block was applied.Confirmed
- 04If it says "SignatureException: Signature length not correct", log in to your router and disable any feature that intercepts connections, or ask your ISP what it is doing.Confirmed
- 05If client.log instead shows "Error loading RS!" with "SocketTimeoutException: timeout", reset your network or improve the connection, since the connection is timing out.Confirmed
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