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GitHub Unreachable or Slow: Six Troubleshooting Methods for 2026

About 1159 wordsAbout 4 min

GitHubConnectivityDNSProxy

...

2026-02-15

GitHub may fail to load, time out, omit images, or clone very slowly because of a GitHub incident, DNS resolution, a firewall, a proxy, a corporate policy, route congestion, or local network configuration. The right fix depends on which layer is failing.

Start with evidence

GitHub's official troubleshooting guide says firewalls, proxy servers, company networks, and other network configurations are common causes. Do not assume every failure is DNS poisoning, and do not paste an arbitrary IP address into your hosts file before testing.

1. Check GitHub and Identify the Failing Layer

First check GitHub Status. Then test the website, DNS, HTTPS, Git over HTTPS, and SSH separately:

# DNS resolution
nslookup github.com

# HTTPS reachability and certificate negotiation
curl -I --connect-timeout 10 https://github.com/

# Git over HTTPS, without cloning a full repository
git ls-remote https://github.com/git/git.git HEAD

# SSH authentication path
ssh -vT git@github.com

Interpret the result:

  • If DNS returns no address, focus on the resolver.
  • If DNS succeeds but HTTPS times out, investigate routing, a firewall, or a proxy.
  • If the website works but git clone fails, inspect Git's remote URL and proxy configuration.
  • If HTTPS works but SSH on port 22 times out, use HTTPS cloning or GitHub's SSH-over-443 endpoint.
  • If only one network fails, contact that network's administrator or provider.

Avoid using ping alone as the verdict. ICMP may be filtered even when HTTPS works.

2. Fix DNS Resolution

Compare the configured resolver with a trusted resolver:

nslookup github.com
nslookup github.com 1.1.1.1

Different answers are not automatically evidence of tampering: GitHub and its content-delivery infrastructure can return different addresses by location and time. A failure, obviously unrelated address, or repeatable mismatch accompanied by connection errors deserves further investigation.

Encrypted DNS can protect DNS queries from alteration in transit. Cloudflare documents its DNS-over-HTTPS endpoint as:

https://cloudflare-dns.com/dns-query

In Chrome or Edge, search the privacy and security settings for “Use secure DNS,” then choose a provider you trust. System and browser behavior varies, and encrypted DNS fixes only the name-resolution layer; it cannot repair an IP-level block, a broken route, or a corporate firewall.

After changing DNS, clear stale cache entries where appropriate:

# Windows
ipconfig /flushdns
# macOS
sudo dscacheutil -flushcache
sudo killall -HUP mDNSResponder

On Linux, the command depends on the active resolver. For systemd-resolved:

sudo resolvectl flush-caches

3. Avoid Hard-Coded GitHub Hosts Entries

The original Chinese article supplied fixed IP addresses for github.com and related hosts. That advice is fragile in 2026. GitHub states that its IP addresses change over time, does not recommend allowlisting by IP, and says the Meta API list is not exhaustive.

If an administrator must maintain an allowlist, monitor the GitHub Meta API and follow GitHub's IP-address guidance. Do not copy old addresses from a blog or IP-lookup site.

If you previously added GitHub entries to the hosts file, temporarily comment them out and test normal DNS again:

  • Windows: C:\Windows\System32\drivers\etc\hosts
  • macOS and Linux: /etc/hosts

Static mappings may send traffic to an obsolete or inappropriate edge address. Never disable TLS verification to compensate for certificate errors.

4. Switch the Git Transport

If SSH port 22 is blocked, HTTPS is often the simplest option:

git remote -v
git remote set-url origin https://github.com/OWNER/REPOSITORY.git
git ls-remote origin HEAD

If you need SSH, GitHub officially supports SSH over port 443:

ssh -T -p 443 git@ssh.github.com

If that succeeds, add the following to ~/.ssh/config:

Host github.com
    Hostname ssh.github.com
    Port 443
    User git

Verify any first-use host-key prompt against GitHub's published SSH fingerprints.

5. Configure an Authorized Proxy Carefully

Where local law and network policy permit it, an authorized proxy or VPN can provide a working route when direct traffic is blocked. For a local HTTP proxy listening on port 7890, Git can be configured with:

git config --global http.proxy http://127.0.0.1:7890

Inspect and remove the setting when it is no longer needed:

git config --global --get http.proxy
git config --global --unset http.proxy

The Git option is named http.proxy and applies to HTTP and HTTPS remotes handled by libcurl; a separate https.proxy key is usually unnecessary. Do not embed a reusable password in a command or configuration file. On managed networks, ask the administrator for the approved proxy and certificate configuration.

For client setup, see:

6. Treat Mirrors and “Accelerators” as Third Parties

The FastGit and CNPMJS examples in the original article are stale, and third-party mirror availability changes frequently. More importantly, a mirror or download proxy can observe requested repository paths and may serve modified or outdated content.

If you use a third-party mirror for a public archive:

  • do not sign in with your GitHub credentials;
  • do not send personal access tokens or private-repository URLs;
  • verify release signatures or checksums from an independent official source; and
  • return to the canonical github.com remote before pushing.

Tools such as Watt Toolkit may alter local proxy, certificate, or hosts settings. Use only the project's official distribution, review what it changes, and know how to restore the original configuration.

7. Reset Local Networking Only When Indicated

On Windows, clearing the DNS cache is low impact:

ipconfig /flushdns

Resetting Winsock is broader and can remove custom Layered Service Provider configuration. Use it only when local socket configuration appears damaged, run the terminal as administrator, and restart afterward:

netsh winsock reset

Before a broad reset, test another browser, disable only the suspect extension, check system time, inspect proxy settings, and try another network. Those checks preserve useful evidence and often isolate the cause faster.

  1. Check GitHub Status and reproduce the failure.
  2. Separate DNS, HTTPS, Git-over-HTTPS, and SSH tests.
  3. Remove stale hosts entries and flush only the relevant cache.
  4. Switch between HTTPS and SSH over port 443.
  5. Use an approved proxy only if the direct network path is the problem.
  6. Escalate managed-network blocks to the administrator rather than bypassing policy.

This order avoids the most common mistake in GitHub troubleshooting: changing several network layers at once and no longer knowing which change fixed—or worsened—the problem.