If ipsendwin stops launching after you install Wireshark and Windows reports that wpcap.dll is missing, the recommended fix today is to use Npcap in WinPcap API-compatible mode. Avoid adding several packet-capture drivers at random, because overlapping WinPcap, Win10Pcap, and Npcap installations can make the problem harder to diagnose.
Quick fix
- Close Wireshark and ipsendwin.
- Open Windows Settings → Apps → Installed apps and check whether Npcap is installed.
- Update or reinstall Npcap using the official Wireshark installer or the official Npcap package.
- Make sure Install Npcap in WinPcap API-compatible Mode is enabled.
- Restart Windows, then launch ipsendwin again.
Recent Npcap releases normally enable WinPcap API compatibility by default. Reinstalling with the option explicitly enabled is still useful when an older driver, a damaged installation, or a previous WinPcap-based package is involved.
Why the error appears
Older applications built for the WinPcap API load libraries such as wpcap.dll when they start. Current Windows builds of Wireshark use Npcap as their packet-capture driver. Npcap provides a WinPcap-compatible mode, but an application may fail to find the required DLL when compatibility mode is disabled or packet-capture drivers conflict.
Step-by-step checks
1. Check installed capture drivers
In Installed apps, look for Npcap, WinPcap, and Win10Pcap. Do not install another driver before you know which packages are already present. Multiple capture-driver packages can expose similar DLLs and services.
2. Use an official Npcap package
The official Wireshark Windows installer includes Npcap, which Wireshark requires for live packet capture. Download Wireshark from the official project rather than from a third-party software mirror.
Official Wireshark download
Official Npcap User’s Guide
3. Enable WinPcap API-compatible mode
During Npcap installation, enable Install Npcap in WinPcap API-compatible Mode. According to the Npcap documentation, this mode installs compatible DLLs in the system directory so that applications written for WinPcap can load them.
If ipsendwin still does not start
- Restart Windows after installing Npcap.
- Check whether endpoint-security software quarantined a Npcap DLL or driver.
- Check for an older WinPcap or Win10Pcap installation.
- Reinstall ipsendwin after the capture-driver configuration is stable.
- Confirm that Wireshark can list interfaces and start a capture. If it cannot, troubleshoot Npcap, permissions, and the network-adapter driver first.
Only capture traffic on networks and devices you are authorized to inspect. Company policy or local law may restrict packet capture.
Why the old Win10Pcap workaround was replaced
An earlier version of the Japanese article recommended installing Win10Pcap. Wireshark now recommends Npcap for current Windows systems, so the first troubleshooting step should be updating Npcap and enabling its compatibility mode instead of adding another legacy capture driver.
Updated July 19, 2026 using the official Wireshark and Npcap documentation. Menu labels can differ by software version.
