Why can't SlashImage connect to the optimization service?

2 min read · Last updated June 2026

Optimizing happens on SlashImage's servers, so your site has to reach api.slashimage.com to get a smaller image back. A connection error means that outbound request did not get through - usually your host is blocking outbound connections. Your existing images are unaffected; the image you tried to optimize is left as it was, ready to retry once the connection is sorted out.

What each message means

These are the messages SlashImage shows when it can't reach the service:

  • Could not connect to the optimization service. Your host may be blocking outbound requests. - your server could not reach api.slashimage.com at all (the address could not be looked up, the connection was refused, or HTTPS could not be established).
  • Request timed out - you can retry again. - the request started but did not finish in time. SlashImage waits up to 45 seconds; this often happens with a very large image.
  • Too many requests - please wait a moment and try again. - the service received the request but throttled it due to capacity; this is not a connection failure. SlashImage waits and retries on its own.
  • Could not reach the API. Check your server's outbound network access. - the same problem, shown when you check your key from the Settings page.

What to check

  1. Allow outbound HTTPS to api.slashimage.com. Some hosting plans block servers from making outbound requests. Ask your host to allow outbound HTTPS to api.slashimage.com - this is the most common fix.
  2. Check a security plugin or server firewall. A security plugin or a host firewall can block the call even when general internet access works. Allow api.slashimage.com.
  3. Retry or shrink a timed-out image. A timeout usually means one heavy image. Retry it; if it keeps timing out, turn on resizing so oversized images are scaled down before they are sent. See Does SlashImage resize my large images?.
  4. For "Too many requests", just wait. SlashImage retries on its own, waiting longer each time (about 1 minute, then 5, then 15).

If it's the key, not the connection

If the message mentions your API key being invalid or needing to reconnect, your site reached our servers but the key was not accepted. See How do I fix an invalid or revoked API key?.

See also

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