What is the SOL file format?
.sol files are commonly associated with Macromedia Flash Player version 6 and later - and, after its acquisition of Flash, with Adobe Systems.
Files with the .sol extension store various program settings in a binary format and function similarly to web browser cookies. Flash applications use .sol files to persist user settings and session data. Many web services used .sol files to gather and store user activity data, which could be leveraged to track and monitor behavior across visits - earning them the informal name "Flash cookies." Unlike HTTP cookies, .sol files were stored separately in OS-specific directories and were harder to clear through standard browser privacy tools:
- Windows:
%APPDATA%\Macromedia\Flash Player\#SharedObjects\<random>\<domain>\<swf>\<name>.sol - macOS:
~/Library/Preferences/Macromedia/Flash Player/#SharedObjects/...
Each .sol file is scoped to a specific domain and .SWF file path. Data is serialized using Adobe's Action Message Format: AMF0 for Flash Player 6-8, and AMF3 for Flash Player 9 and later. Flash enforced a 100 KB default storage limit per domain, which could be raised to 10 MB with user consent.
The SOL files management console was available via the Flash Player settings menu. Users could disable .sol file generation for any or selected websites. Some browsers - Firefox, for example - included built-in tools for managing .sol files. Tools such as SOLReader and JPEXS Free Flash Decompiler can display .sol contents and analyze their internal structure.
Adobe Flash Player reached end-of-life on December 31, 2020, and all major browsers blocked Flash in January 2021. New .sol files are no longer created, but existing files may still be present on systems that previously ran Flash.
Security & safety
RISK: LOWSOL files are passive data files with no executable code. Privacy note: they may contain game saves, login tokens, or preferences from Flash-era sites. Safe to delete if you no longer run Flash content. Ruffle's sandboxing means .sol files created by Ruffle carry the same low risk.
Format details
in a nutshell- Solitaire Save File (Microsoft) - Microsoft Solitaire (classic Windows versions) used .sol as its save game format - unrelated to Flash.
Programs that open SOL files
Windows4 apps
SOLReader
Free Open the .sol file in SOLReader to view AMF-decoded key-value pairs. Tool is old but the format hasn't changed.
JPEXS Free Flash Decompiler (FFDec)
Open-source FFDec can open and display .sol files under Tools → Local Shared Object Editor.
Ruffle (Flash emulator)
Open-source Run the original Flash content in Ruffle; it will read/write .sol files in the same location Flash used, preserving save data.
Hex editor (HxD, 010 Editor)
Free SOL files are binary AMF; a hex editor with an AMF template can decode them manually. 
macOS1 app
Ruffle (Flash emulator)
Open-source macOS build available; reads and writes .sol files when running compatible Flash content. 
Linux1 app
Technical details
deep spec| Encoding | Binary (AMF0 or AMF3 serialization) |
| Byte order | Big-endian |
| File magic | 0x00 0xBF at offset 0; ASCII 'TCSO' at offset 4 (bytes 4-7: 54 43 53 4F) |
| Data serialization | AMF0 (Flash Player 6-8) or AMF3 (Flash Player 9+, ActionScript 3) |
| Compression | None - stored uncompressed |
| Encryption | None - data readable with any AMF parser |
| Storage scope | Per-domain and per-SWF path; each .sol is tied to one domain and one SWF file location |
| Default storage limit | 100 KB per domain (Flash Player default); user-expandable to 10 MB via the Flash Player settings panel |
| Typical file size | Under 100 KB (enforced by Flash Player by default) |
| Internal structure | 4-byte length (uint32 BE) + 'TCSO' magic + padding + UTF-8 shared-object name + AMF version flag + AMF key-value pairs + 0x09 end marker |
| MIME type | application/octet-stream (no registered MIME type) |
| Associated OS | Windows, macOS, Linux (wherever Adobe Flash Player ran) |
| Current status | Obsolete - Adobe Flash Player reached end-of-life December 31, 2020; no new .sol files are created |
| Released | 2002 (Macromedia Flash Player 6) |
| Latest version | Last written by Adobe Flash Player 32 (EOL December 31, 2020) |
| Specification | rtmp.veriskope.com |
SOL conversions
Community Q&A
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