What is the DTF file format?
.dtf files are associated with the ACDSee image viewer, developed by ACD Systems International Inc.
.dtf files store thumbnail images in the form of a per-folder binary database. The files are loaded by ACDSee alongside the images in a folder, caching small JPEG-compressed preview images plus basic metadata so the application can display a folder's contents quickly without regenerating previews on each visit. .dtf files are not directly accessible inside ACDSee - they function purely as an internal cache.
Frequent use of ACDSee may generate large .dtf files which in turn can impact application performance by significantly slowing thumbnail loading times. Should such a situation occur, you may safely delete the .dtf file - ACDSee will simply rebuild it on the next folder visit, leaving the original photos untouched. Deleting the file should significantly improve ACDSee's performance. .dtf files are saved in each image folder alongside a companion .ddf descriptions file; ACDSee's folders are typically located in the user's Documents or AppData directory.
The per-folder .dtf cache is a legacy format from older ACDSee releases. Modern ACDSee Photo Studio replaced it with a centralized .dbin database approach, so .dtf files are mainly encountered on older Windows installations or in archived photo collections.
Security & safety
RISK: LOWAn ACDSee .dtf is a passive cache file - it contains thumbnail images and index data, no executable code, so it is safe. It is also safe to DELETE: ACDSee rebuilds it and your original photos are untouched. The only practical caution is identity confusion - make sure a .dtf you care about is the ACDSee cache and not a Symantec Q&A database (which IS a real data document you would not want to lose). Be wary, as always, of unexpected files from untrusted sources, but a normal ACDSee .dtf in your own picture folder is harmless clutter.
Format details
in a nutshell- Symantec Q&A Database (.dtf) - Data file of the 1980s-90s Symantec Q&A flat/relational database (with a companion .idx index); openable today via Lantica Sesame, which can import Q&A .dtf files.
- DESQview Font / DESQview file - Legacy file associated with Quarterdeck's DESQview DOS multitasker; obsolete and unrelated to image software.
Programs that open DTF files
Windows1 app
ACDSee Photo Studio
Paid ACDSee creates and uses the .dtf cache automatically while browsing a folder - there's nothing to 'open' manually. Just browse the image folder in ACDSee; it reads/refreshes the cache for you. Technical details
deep spec| Developer | ACD Systems International Inc. |
| Format type | Proprietary binary per-folder thumbnail and metadata cache database |
| Byte order | Little-endian |
| File encoding | Binary |
| Associated OS | Windows |
| MIME type | application/octet-stream |
| Thumbnail compression | Embedded JPEG-compressed preview images |
| Thumbnail color depth | 24-bit RGB (JPEG previews) |
| Thumbnail dimensions | Small fixed previews, typically up to a few hundred pixels per side |
| Typical file size | Tens of KB to several MB, depending on the number of images in the folder |
| File signature | No publicly documented magic bytes; identified by filename and folder context |
| Cache scope | Per-folder - one .dtf file per image folder visited in ACDSee |
| Companion file | .ddf descriptions file stored alongside .dtf in the same image folder |
| Deletability | Safe to delete; ACDSee regenerates the file automatically on the next folder visit |
| Superseded by | ACDSee centralized database (.dbin and related formats) in modern ACDSee Photo Studio versions |
| Released | Late 1990s / early 2000s (older ACDSee versions; per-folder cache files) |
| Latest version | Legacy - superseded by ACDSee's centralized .ddf/.dbin database in modern versions |
| Specification | www.acdsee.com |
DTF conversions
Community Q&A
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