What is the QDF file format?
.qdf files store data used by Quicken, a personal finance software developed by Intuit for managing financial data and retrieving account information (transactions, balances, and more). Quicken allows users to manage personal or small-business budgets. Advanced versions of Quicken offer features such as investment portfolio management and integration with financial services offered by various institutions such as banks. Since 2018, Quicken operates as a subscription product; .qdf remains the primary data file for Quicken on Windows.
Data redundancy
Quicken supports a data redundancy system built around .qdf files. The program saves all accounts, transactions, categories, budgets and investments in the main .qdf database and automatically creates several companion files in the same folder - including .qel (attachments and log), .qph (price history) and .qtx - along with a .qdf-backup file. These sibling files store pieces of data copied from the main .qdf as a means of providing data redundancy and integrity. In case of data corruption or accidental data deletion, the main file can be restored based on the subfiles and vice versa. This mechanism helps keep sensitive financial data safe and makes working with Quicken a smoother experience. When moving or backing up, always copy the whole folder rather than the .qdf file alone.
The .qdf format is a proprietary binary database with no publicly documented magic bytes, opened only by the same or a newer version of Quicken that created it. The file can optionally be password-protected within Quicken. For data exchange with other tools, Quicken can export to .QIF or .QFX formats.
Security & safety
RISK: LOWA .qdf is a passive data file, not executable, so it can't run code. The real risks are about your data, not malware: the .qdf is your entire financial history, so back it up (and its .qdf-backup/.qph/.qel siblings) and keep it secure - it can hold account numbers and balances. Optionally enable Quicken's password protection. Avoid uploading a .qdf to untrusted online "QDF viewer/converter" sites: there is no real web viewer for this proprietary format, so such pages are typically scams or data-harvesting traps. Use Quicken's own export for portable copies.
Format details
in a nutshellPrograms that open QDF files
Windows3 apps
Quicken
Paid File > Open and select the .qdf (use the same or a newer Quicken version than created it). This is the only program that truly opens a .qdf. 
Quicken - Validate & Repair
Paid If the .qdf won't open or looks damaged, use File > Validate and Repair File (or restore the .qdf-backup) before anything else.
ProperSoft Transactions / QIF2CSV (data export route)
Paid Not a .qdf reader: first export QIF/CSV from Quicken, then use ProperSoft tools to convert that to CSV/Excel/other formats. Technical details
deep spec| Developer | Intuit Inc. |
| Format type | Proprietary binary database |
| Byte order | Little-endian |
| Compression | Internal (Quicken-managed) |
| Encryption | Optional password protection, configured within Quicken |
| Platform | Windows only; Quicken for Mac uses its own separate package format |
| Typical file size | A few MB to several hundred MB, growing with years of transactions and attachments |
| Companion files | `.qel` (attachments/log), `.qph` (price history), `.qtx`, and `.qdf-backup` - all stored alongside `.qdf` in the same folder |
| MIME type | `application/x-quicken` (unofficial); generic fallback `application/octet-stream` |
| Magic bytes | None publicly documented; proprietary format with no known public file signature |
| Version compatibility | Newer Quicken can upgrade and open older `.qdf` files; older Quicken cannot open a `.qdf` created by a newer version |
| Stored data | Accounts, transactions, categories, budgets, investment portfolios, price history, attachments and application settings |
| Export paths | Quicken can export data to `.QIF` or `.QFX` for use with other financial applications |
| Integrity tool | Built-in `File > Validate & Repair` function in Quicken checks and fixes the `.qdf` database |
| Released | Quicken for Windows (1990s); current primary data-file extension for Quicken Windows |
| Latest version | Quicken (subscription, 2018+); data-file structure evolves per release |
| Specification | www.quicken.com |
QDF conversions
Community Q&A
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