iftop
iftop is free Linux software that displays current bandwidth usage between pairs of hosts on a network interface.
What iftop is
iftop is free Linux software that displays current bandwidth usage between pairs of hosts on a network interface. It listens on a named interface or chooses the first interface it recognizes as external when none is specified. Sufficient permissions are required to monitor all traffic on that interface. The terminal view can show host names, ports, bandwidth bars, totals, and rates averaged over 2, 10, and 40 seconds. Packet filter code changes what is captured, while display filters only change what appears. Configuration can come from a file, defaulting to ~/.iftoprc. Options include an IPv4 network boundary, link-local IPv6 traffic, and promiscuous mode for traffic between other hosts on the same network segment. A text interface without ncurses can print one report after a chosen interval and limit line count. The software is free under the GNU General Public License version 2 or later and is provided without warranty. After a capture-filter change, entries from the recent capture window may remain visible for up to 40 seconds. The manual names Paul Warren as author.
Good
- Free GPL-licensed Linux software
- Shows host pairs and bandwidth rates
- Supports packet and display filters
- Text mode works without ncurses
- Promiscuous capture mode available
Watch out
- Requires sufficient monitoring permissions
- Application monitoring is not provided
- Recent entries may remain for up to 40 seconds
- Provided without warranty
Who it suits
iftop suits Linux users who need a terminal view of bandwidth between network hosts. It is useful when packet and display filtering or short text reports are required.
Verdict
iftop is a focused command-line bandwidth monitor for Linux interfaces. Its filtering, averaging, configuration, and text-output options support several terminal workflows, but it requires appropriate permissions and does not provide application monitoring.
Plans and prices
From iftop's own pricing page, checked 4 Oct 2026.
| Plan | Price | What it gives you |
|---|---|---|
| iftop | Free | GPL-licensed software; requires sufficient permissions to monitor network traffic on the interface |
The facts
Each one read from iftop's own pages, with the date it was checked.
What it does
- Configuration
- iftop can read settings from a configuration file, defaulting to ~/.iftoprc when no alternate file is specified.checked 4 Oct 2026
- Filtering
- It supports packet filter code and display filters, with display filters affecting what is shown rather than what is captured.checked 4 Oct 2026
- Integration
- The manual lists tcpdump, pcap, and driftnet as related tools; it does not state integrations with external services.checked 4 Oct 2026
- Network support
- Configuration options include an IPv4 network boundary and display of link-local IPv6 traffic.checked 4 Oct 2026
- Notable limitation
- After changing the capture filter, existing display entries may remain for up to 40 seconds because the display reflects a recent capture window.checked 4 Oct 2026
- Permissions
- iftop must be run with sufficient permissions to monitor all network traffic on the interface.checked 4 Oct 2026
- Promiscuous mode
- iftop can put the interface into promiscuous mode to capture traffic between other hosts on the same network segment.checked 4 Oct 2026
- Purpose
- iftop displays current bandwidth usage by pairs of hosts on a network interface.checked 4 Oct 2026
- Security and license
- The manual identifies iftop as free software under the GNU General Public License, version 2 or any later version, and provides it without warranty.checked 4 Oct 2026
- Terminal output
- A text interface without ncurses is available, with options to print a single output after a specified number of seconds and limit the number of lines.checked 4 Oct 2026
- Traffic capture
- iftop listens on a named interface or, if none is specified, the first interface it finds that looks like an external interface.checked 4 Oct 2026
- Traffic views
- The display can show host names, port numbers, bandwidth bars, totals, and traffic rates averaged over 2, 10, and 40 seconds.checked 4 Oct 2026
The company
- Maker
- The manual names Paul Warren as the author.checked 4 Oct 2026
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