Hex Packet Decoder | IP Checksum Calculator

Hex packet decoder for tcpdump and Wireshark dumps. Decodes Ethernet, VLAN, IPv4, IPv6, TCP, UDP and ICMP headers and verifies each checksum. Free.

Also known as: hex packet decoder · hex packet decoder online · ip header checksum calculator · ipv4 header decoder · ipv4 checksum calculator · tcp header decoder · packet hex dump decoder · tcpdump hex decoder · wireshark hex dump decoder · ethernet frame decoder

network tools

hashing and checksum tools

encoding and decoding tools

networking

Hex Input

Packet starts at

Decoded Layers

Decoded Ethernet, VLAN, ARP, IPv4, IPv6, TCP, UDP, ICMP and ICMPv6 headers, with every checksum verified, appear here.

About Hex Packet Decoder

Hex Packet Decoder is used to read raw packet bytes copied from tcpdump, Wireshark or a log when you need to know exactly what was on the wire. It splits a frame into Ethernet, VLAN, ARP, IPv4, IPv6, TCP, UDP, ICMP and ICMPv6 headers, shows every field with its byte offset, decodes IP and TCP options, and recomputes each checksum. Nothing leaves your browser.

Key Features

Reads tcpdump -X and -XX output, Wireshark and tshark hex dumps, xxd, hexdump -C, C arrays, Python bytes and plain hex
Decodes Ethernet II, 802.1Q and 802.1ad VLAN tags, MPLS, Linux cooked captures (SLL and SLL2), ARP, IPv4 and IPv6 with extension headers
Verifies the IPv4 header checksum and the TCP, UDP, ICMP and ICMPv6 checksums, and shows the correct value when one is wrong
Decodes IPv4 options (Record Route, Timestamp, source routing, Router Alert) and TCP options (MSS, window scale, SACK, timestamps, MPTCP)
Flags truncated headers, malformed option lengths, Ethernet padding and scan-style TCP flag combinations at the layer where they occur
Decodes several packets at once when a dump holds more than one

Use Cases

Read a SYN from a tcpdump capture on an EC2 instance in us-east-1 to see its MSS, window scale and options
Check whether packets hitting a server carry IPv4 options before applying the CVE-2026-98432 firewall rule
Recompute the IPv4 header checksum by hand for a networking course or a CCNA lab
Decode the hex bytes an IDS alert or a firewall log prints for a dropped packet
Debug a raw socket, DPDK or eBPF program by pasting the bytes it sends
Tell checksum offload from real corruption when a capture shows bad TCP checksums

Supported Formats

tcpdump -X / -XX

Wireshark hex dump

tshark -x

xxd

hexdump -C

Plain hex stream

C array

Python bytes

Ethernet II

802.1Q / 802.1ad

Linux SLL / SLL2

IPv4 / IPv6

TCP / UDP

ICMP / ICMPv6

Related Keywords

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How is the IPv4 header checksum calculated?

Set the checksum field to zero, split the header (20 bytes plus any options) into 16-bit words, and add them with one's complement arithmetic: whenever a sum overflows 16 bits, wrap the carry back into the low bits. The checksum is the bitwise NOT of that sum. A receiver adds every word including the stored checksum, and a correct header sums to 0xFFFF. TCP and UDP use the same algorithm over a pseudo-header (source address, destination address, protocol and length) plus the whole segment, which is why a wrong address or length breaks the TCP checksum even when the TCP bytes are intact. UDP over IPv4 may send 0x0000 to mean no checksum; IPv6 requires one. Captures taken on the sending machine often show bad TCP and UDP checksums because the network card fills them in after the capture point, a feature called checksum offload.

Privacy & Security

All processing happens locally in your browser. Your data never leaves your computer, ensuring complete privacy and security.

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Frequently asked questions

What is Hex Packet Decoder used for?

Hex packet decoder for tcpdump and Wireshark dumps. Decodes Ethernet, VLAN, IPv4, IPv6, TCP, UDP and ICMP headers and verifies each checksum. Free.

Is Hex Packet Decoder free to use?

Yes. Hex Packet Decoder is completely free with no usage limits, and there is no paid tier required to use it.

Do I need an account to use Hex Packet Decoder?

No. Hex Packet Decoder works immediately in your browser with no signup, login, or email address required.

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