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Nesalizer

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What Nesalizer is

Nesalizer is a free, open-source NES emulator for Linux/POSIX, with an experimental Windows port. It is a work-in-progress project without a graphical interface. Its main feature is real-time rewind: the emulator keeps one state per frame in a ring buffer, restores those states backward, and plays buffered audio in reverse. A 30-minute rewind history uses about 1.3 GB of memory for most games because states are not compressed. Save states remain in memory and are not written to disk. Nesalizer supports iNES mapper numbers 0, 1, 2, 3, 4, 5, 7, 9, 10, 11, 13, 28, 71, and 232, which the README says covers most ROMs. PAL and NTSC are supported, with NTSC ROMs recommended. Keyboard controls are hardcoded. SDL2 is the only stated final-output dependency. Movie recording is broken because of libav changes. The project uses GPLv2 and welcomes bug reports and contributions.

Who it suits

Nesalizer suits users wanting an open-source NES emulator with rewind on Linux/POSIX. It may also suit Windows users willing to try an experimental port and keyboard controls.

What it does well

  • Real-time rewind reverses gameplay and audio
  • Supports PAL and NTSC systems
  • Covers many listed iNES mapper numbers
  • SDL2 is the only stated dependency
  • GPLv2 project welcomes contributions

What to know first

  • No graphical interface is provided
  • Rewind uses about 1.3 GB for 30 minutes
  • Save states are not saved to disk
  • Movie recording is currently broken

Limits

Rewind history is held in memory; a 30-minute buffer uses around 1.3 GB for most games. Save states remain in memory rather than being stored on disk, and movie recording is broken.

Getting started

  1. Use a Linux/POSIX system or try the experimental Windows port
  2. Install SDL2 as the stated final dependency
  3. Build Nesalizer using the project’s provided commands
  4. Load a supported NES ROM
  5. Use the hardcoded keyboard mappings to play and rewind

Verdict

Nesalizer focuses on frame-based rewind, including reversed audio, while supporting a broad set of listed NES mappers. Its lack of GUI, memory-heavy rewind buffer, in-memory saves, and experimental Windows status are important limitations.

Questions

What does Nesalizer cost?

Nesalizer is free and open source under the GPLv2 license.

Which operating systems are supported?

The project currently requires a *nix system, with Linux/POSIX support. A contributor’s Windows port is described as experimental.

How does rewind work?

The emulator stores one emulation state per frame in a ring buffer, loads states in reverse order, and plays audio backward.

Which NES formats are supported?

Nesalizer supports iNES mapper numbers 0, 1, 2, 3, 4, 5, 7, 9, 10, 11, 13, 28, 71, and 232. Both PAL and NTSC are supported, with NTSC ROMs recommended.

Are save states permanent?

No. Save states are held in memory and are not saved to disk.

Does it include a graphical interface?

No. The project says it still lacks a GUI.

Facts from Nesalizer's own pages

Audio
During rewind, audio is added in reverse from the end of the audio buffer. · github.com, 8 Oct 2026
Build dependency
SDL2 is the only dependency for final output. · github.com, 8 Oct 2026
Compatibility
The README lists supported iNES mappers as 0, 1, 2, 3, 4, 5, 7, 9, 10, 11, 13, 28, 71, and 232. · github.com, 8 Oct 2026
Controls
Controls are hardcoded and include keyboard mappings for the D-pad, A, B, Start, Select, rewind, save/load state, and reset. · github.com, 4 Oct 2026
Interface
The emulator lacks a GUI and its controls are hardcoded. · github.com, 8 Oct 2026
License
The project is licensed under GPLv2. · github.com, 8 Oct 2026
Memory use
A 30-minute rewind buffer uses around 1.3 GB of memory for most games, and states are not compressed. · github.com, 4 Oct 2026
Movie recording
Built-in movie recording support is described as broken due to libav changes. · github.com, 4 Oct 2026
Operating system
The project says it currently requires a *nix system and provides Ubuntu build commands. · github.com, 8 Oct 2026
Performance
The author reports about 6× emulation speed on a single core of an older Core i7 2600K. · github.com, 4 Oct 2026
Platforms
The README says a *nix system is currently required and describes an experimental Windows port by a contributor. · github.com, 4 Oct 2026
Purpose
Nesalizer is a work-in-progress NES emulator with real-time rewind that correctly reverses sound. · github.com, 8 Oct 2026
Rewind
It stores emulator state once per frame in a ring buffer and loads states in reverse order during rewind. · github.com, 8 Oct 2026
Rewind memory
A 30-minute rewind buffer uses around 1.3 GB of memory for most games, and states are not compressed. · github.com, 8 Oct 2026
Save states
Save states are in memory and are not saved to disk; persistent on-disk save states are listed as missing. · github.com, 8 Oct 2026
Support
The README invites bug reports and contributions and provides the author's email in reversed form. · github.com, 4 Oct 2026
Support and contributions
The author invites users to report issues and contribute to the project. · github.com, 8 Oct 2026
TV systems
Both PAL and NTSC are supported, and the README recommends NTSC ROMs. · github.com, 4 Oct 2026
Video standards
It supports both PAL and NTSC, and the README recommends NTSC ROMs. · github.com, 8 Oct 2026
Windows status
The README describes a quick-and-dirty experimental Windows port by a contributor. · github.com, 8 Oct 2026

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