Fix Slack Error 408 Request Timeout (2025)

Updated: 11/29/2025

You try to upload a file, post a message, or call the Slack API from your app, and instead of a clean response you see 408 Request Timeout in the logs or in an error popup. Sometimes the file still appears in the channel, other times nothing shows up and your integration silently fails. This status means Slack servers did not receive the full request in time or the response took longer than your client was willing to wait, usually due to slow networks, large uploads, or tight timeout settings [web:31][web:34][web:40].

Method 1: Fix Local Network And Client Timeouts

Because Error 408 is fundamentally a timing problem, the first step is to make sure your connection to Slack is stable and that your client is not giving up too early [web:28][web:34][web:40].

Step 1: Test Your Connection Outside Slack

On the affected machine, open another real time service such as a video call, a streaming site, or another chat app and see if it stutters at the same time Slack does. If everything lags together or drops periodically, the problem is your internet connection, not Slack, and you should restart your modem and router or switch to a more stable network [web:34].

Step 2: Restart Router And Switch To Wired If Possible

Unplug your modem and WiFi router for at least thirty seconds, then plug them back in and wait for all lights to stabilize before trying Slack again. If you can, connect your computer with an Ethernet cable instead of WiFi, which eliminates signal drops that often cause long running uploads to hit client side timeouts [web:34].

Step 3: Increase Timeout In Custom Integrations

If you are using the official Slack SDK in your own code, such as the Python or Node client, raise the timeout parameter from a few seconds to a safer window like 60 to 300 seconds for large file uploads or slow servers, then redeploy your app and retest. This gives Slack more time to process the request and reduces false 408 errors that appear even after successful uploads [web:31][web:37][web:40].

Method 2: Reduce Payload Size And Frequency

Even on a decent network, trying to send too much data at once, or too many requests in a burst, makes it more likely that Slack or your own infrastructure will hit a 408 timeout condition [web:31][web:34].

Step 1: Compress Or Split Large Files

When uploads fail partway through with Error 408, compress the file into a smaller archive or split big assets into several smaller pieces before uploading. Smaller files finish much faster and are less likely to be interrupted by momentary drops or time limits on proxies and gateways between you and Slack [web:31].

Step 2: Avoid Back to Back Heavy API Calls

If your bot or app posts multiple large messages or file uploads at once, add a small delay between them so they do not all compete for bandwidth simultaneously. Throttling your own traffic a little can keep each request under the timeout threshold instead of overwhelming the connection [web:34][web:40].

Step 3: Move Non Critical Work Off The Request Path

In slash commands or interactive components, do only the minimum necessary work before responding to Slack and move heavy processing into asynchronous jobs. Responding quickly with a placeholder message and then updating it later prevents Slack from timing out the original request [web:40].

Method 3: Check Workspace Limits And Slack Status

In corporate environments, firewalls, SSL inspection, or outbound proxies can delay or disrupt connections enough to trigger request timeouts. Share recent timestamps and any relevant error logs with your IT team so they can look for blocked or delayed connections to Slack endpoints and whitelist them if necessary [web:34][web:40].