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Head-to-head · Fuzz Testing Software

AFL++ vs syzkaller

  • Updated Oct 2026
  • Both researched from official sources
  • 4 checks side by side
Higher score AFL++ #4 in Fuzz Testing Software 8.7/10 Free plan Free plan✓ 3 of 3 features Visit AFL++
syzkaller #8 in Fuzz Testing Software 8.1/10 Open source ✓ 3 of 3 features Visit syzkaller

AFL++ leads on 0 checks, syzkaller on 0, and 4 are even. Who comes out ahead on the 4 yes/no, price and count checks where we have data for both products. The editor score weighs everything else too.

Our verdict

  • Highest scoreAFL++ · 8.7/10
  • Free planonly AFL++

AFL++ scores higher on our rubric for fuzz testing software: 8.7 against 8.1 out of 10; our editors rank them #4 and #8.

AFL++ is the better fit for general-purpose native and binary fuzzing. syzkaller is the better fit for operating-system kernel fuzzing.

  • AFL++ fits best

    General-purpose native and binary fuzzing

  • syzkaller fits best

    Operating-system kernel fuzzing

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Side by side

Feature AFL++ 8.7/10 Visit ↗ syzkaller 8.1/10 Visit ↗
At a glance
Editor score 8.7 8.1
Ranking #4 in Fuzz Testing Software #8 in Fuzz Testing Software
Best for General-purpose native and binary fuzzing Operating-system kernel fuzzing
Pricing model Free Free
Starting price Free plan Open source
Free plan ✓ (best) Not checked yet
Free trial — —
Deployment Self-hosted Self-hosted
Platforms Linux, macOS, Android, Windows Linux, Windows, macOS
Support Community, Docs Community, Docs
Built for Solo, Small business, Mid-market, Enterprise Small business, Mid-market, Enterprise
Features AFL++ 3/3 · syzkaller 3/3
Coverage guidance ✓ ✓
Crash triage ✓ ✓
CI/CD support ✓ ✓
Specs
Input generation methods mutation generation, mutation
Target types source-code targets, binary-only targets, file inputs, stdin inputs, Android native libraries, Win32 PE binaries operating-system kernels and syscall interfaces: FreeBSD, Fuchsia, gVisor, Linux, NetBSD, OpenBSD, Windows
Execution mode Local Local
Supported languages C, C++, Python, Rust Not checked yet
Our review
Pros
  • Supports source and binary-only fuzzing across four platforms
  • Combines persistent execution, custom mutators, and parallel fuzzing
  • Includes crash triage, minimization, dictionaries, and CI support
  • Generates and mutates syscall programs with coverage guidance
  • Runs against virtual machines or physical devices
  • Reproduces, minimizes, stores, and deduplicates kernel crashes
Cons
  • Local execution puts setup and operations on the user
  • Its primary focus is native programs and selected binary targets
  • Mutation-based input generation may not suit every testing strategy
  • Focused on operating-system kernels rather than general application fuzzing
  • Requires teams able to build and instrument target kernels
  • Local execution may demand kernel and device infrastructure
Our verdict

AFL++ is an open-source, coverage-guided fuzzer for developers and security researchers testing programs and libraries. It targets file-processing programs, command-line tools, native libraries, and selected binary targets. Supported…

Read the review →

syzkaller is an open-source, unsupervised coverage-guided fuzzer for operating-system kernels. It generates and mutates syscall programs, executes them through virtual machines or physical devices, collects kernel code coverage, and…

Read the review →
  1. AFL++Fuzz Testing Software 8.7Free plan
  2. syzkallerFuzz Testing Software 8.1Open source

Strengths and trade-offs

  • AFL++ — where it wins

    • Supports source and binary-only fuzzing across four platforms
    • Combines persistent execution, custom mutators, and parallel fuzzing
    • Includes crash triage, minimization, dictionaries, and CI support

    Where it doesn't

    • Local execution puts setup and operations on the user
    • Its primary focus is native programs and selected binary targets
    • Mutation-based input generation may not suit every testing strategy

  • syzkaller — where it wins

    • Generates and mutates syscall programs with coverage guidance
    • Runs against virtual machines or physical devices
    • Reproduces, minimizes, stores, and deduplicates kernel crashes

    Where it doesn't

    • Focused on operating-system kernels rather than general application fuzzing
    • Requires teams able to build and instrument target kernels
    • Local execution may demand kernel and device infrastructure

More comparisons

All fuzz testing software comparisons → · Full ranking →

Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026

Last updated · How we research and update