What is the MRC file format?
The .mrc file extension is used by script files for mIRC, an Internet Relay Chat (IRC) client application for Windows developed by Khaled Mardam-Bey of mIRC Co. Ltd. .mrc files store instructions for mIRC in the form of plain-text scripts written in the mIRC Scripting Language (MSL).
What are .mrc files used for?
Instructions stored in .mrc files are commonly used for automating tasks performed in mIRC, including opening new chat windows, or securing users and channels from spam or message flooding. .mrc script files can also be used for creating add-ons that extend mIRC's functionality - for example, bots, simple games, or custom command aliases. More advanced scripts combine alias definitions, on-event handlers such as on JOIN or on TEXT, dialog definitions, and remote commands to build full-featured IRC tools.
Creating .mrc files
.mrc files are generated with the mIRC Scripts Editor (opened with Alt+R), a dedicated built-in tool for writing mIRC scripts and instructions. Because the format stores its content as plain text (MIME type text/plain), any standard text editor can open and modify .mrc files as well. Scripts are organized into named sections using square-bracket headers such as [aliases] or [events]; mIRC reads these at startup by consulting its scripts.ini file. Settings and preferences are kept separately in INI files such as mirc.ini, which sit alongside the .mrc script files.
Security & safety
RISK: MEDIUMmIRC scripts execute real commands - they can join channels, message users, read/write files on your PC, download data, and (via certain identifiers) launch programs. A malicious .mrc loaded into mIRC can therefore harm your system or hijack your IRC identity, and IRC has a long history of trojan/"script kiddie" payloads spread this way. Always open an .mrc in a text editor and review it before loading, and only load scripts from sources you trust. Note: this risk is specific to the mIRC-script meaning - a cryo-EM .mrc image is passive data and not executable.
Format details
in a nutshell- MRC electron-microscopy image/map (CCP-EM) - An entirely different binary 3D image format - an industry standard in cryo-electron microscopy/tomography (density maps); opened in ChimeraX/IMOD, not mIRC.
- Mixed Raster Content image (JPEG 2000 / PDF MRC) - A compression model that splits a scanned page into text/background layers; appears inside container files, not usually as a loose .mrc.
Programs that open MRC files
Windows2 apps
mIRC
Paid Tools → Scripts Editor → File → Load (or type /load -rs file.mrc) to install the script. mIRC is the program that actually runs it (shareware, paid after trial). 
Notepad / VS Code
Free Open the .mrc to read or edit the script source as plain text - always review a script here before loading it into mIRC. 
macOS1 app
Text editor (TextEdit / VS Code)
Free View/edit the .mrc as text. (mIRC itself is Windows-only - to run a script you'd need mIRC under Wine/CrossOver or a Windows VM.) 
Linux1 app
Text editor
Built-in Read/edit the script as text; mIRC runs via Wine if you actually need to execute it. Technical details
deep spec| Script language | mIRC Scripting Language (MSL), an interpreted, event-driven scripting language built into mIRC |
| Language constructs | alias definitions, `on`-event handlers (e.g. `on JOIN`, `on TEXT`), `dialog` definitions, and remote commands |
| File encoding | ANSI/Windows-1252 in older mIRC versions; UTF-8 supported from mIRC 7.x onward |
| File identification | No magic bytes; plain-text content recognized by section headers such as `[aliases]` or `[events]` |
| MIME type | `text/plain` |
| Section format | Sections delimited by square-bracket headers, e.g. `[aliases]`, `[events]`, `[script]` |
| Execution model | Interpreted at runtime by mIRC's built-in script engine; not compiled to bytecode |
| Platform | Windows only (mIRC is a Windows-exclusive IRC client application) |
| Automatic backup | mIRC creates `.mrc.bak` backup copies before overwriting existing script files |
| Startup loading | Loaded via `scripts.ini`, which lists `.mrc` files mIRC imports at application startup |
| Developer | mIRC Co. Ltd., maintained by Khaled Mardam-Bey |
| Related configuration | mIRC settings stored in `.ini` files (e.g. `mirc.ini`, `scripts.ini`) alongside `.mrc` script files |
| Built-in editor | mIRC includes a built-in Scripts Editor (Alt+R) for writing and debugging `.mrc` files |
| Released | 1995 (mIRC's scripting/remote 'mrc' files) |
| Specification | www.mirc.com |
MRC conversions
Community Q&A
asked by usersNo questions yet - be the first to ask about MRC files.
