What File Format Should You Use to Keep a Diary for Ten Years?
For a text-first diary, keep each entry as UTF-8 plain text (.txt) or in a clearly documented, widely used text format, and store the files in folders that are easy to copy and open. If preserving the page’s appearance matters, also export a PDF/A copy. A format alone cannot protect ten years of writing: keep more than one independent copy and check that the files still open and read correctly. This guide is for someone choosing how to save a personal digital diary for later reading. The practical recommendation adapts institutional guidance for collections to an individual archive; no format can guarantee that files will remain accessible indefinitely.
Start with what you want to preserve
A diary entry has at least two useful qualities: its words and, sometimes, its appearance. Plain text keeps the words in a simple, portable form, but it does not preserve page layout, fonts, or images. A page-oriented format can retain more of that presentation, but may be more complex to create and validate.
The Library of Congress’s Recommended Formats Statement for textual works ranks UTF-8 first among its preferred character encodings for digital text. For formats, it lists XML-based markup, EPUB and selected page-layout formats—including PDF/A—among preferred options; plain text is in its “other formats” category. This is guidance for materials submitted to a major library, not a direct verdict on an individual diary. It does show why “plain text is always the archival best” would be too broad: structure and presentation can matter, and the right choice depends on the content.
For an ordinary text diary, UTF-8 plain text is a strong working master because it keeps the entry content straightforward and can be read without the original word processor. That practical adaptation favors simplicity for personal use. If your entries rely on elaborate formatting, embedded photographs, tables, or handwritten marks, plain text by itself will not preserve the whole experience.
Choose a format that matches the diary
What your diary contains: Mostly words, dates, and simple headings; Practical format choice: UTF-8 plain text (.txt); What to keep in mind: Very portable, but layout and rich formatting are lost.
What your diary contains: Headings, links, or simple document structure; Practical format choice: A broadly supported structured format, such as HTML or XML, with its encoding and any needed stylesheets documented; What to keep in mind: Structure can aid organization, but linked styles or other dependencies need to be kept with the entries.
What your diary contains: Carefully composed pages where appearance matters; Practical format choice: Keep the editable source and export a PDF/A copy; What to keep in mind: PDF/A is designed for long-term preservation of page-oriented documents; it does not itself guarantee future access or make the document easy to edit.
What your diary contains: A document created in a word processor; Practical format choice: Keep the original file and make a plain-text or PDF/A access copy, depending on what matters; What to keep in mind: The original may preserve formatting or editing features, but depends more on compatible software.
These choices draw on the Library of Congress’s format guidance, which includes UTF-8, XML-based formats, HTML/XHTML, DOCX/OOXML, ODF, PDF/A, and plain text in different preference categories. The table is a practical adaptation rather than a library ranking for personal diaries. The Library’s PDF/A format description explains the format family; the format sustainability overview discusses why format features and complexity matter over time.
A simple text-first setup
Create one UTF-8 text file per entry, or one file per month if that is easier to manage. Use an unambiguous date in the filename, such as 2026-09-28.txt, and put the same date at the top of the entry. ISO-style year-month-day ordering makes filenames sort chronologically in common file browsers. This is an organizational convention, not a preservation standard.
If you use non-Latin characters, accents, or emoji, check a few entries on another device or text editor before settling on the workflow. UTF-8 is widely supported, but the important practical check is that the characters actually appear as intended after reopening or copying the file. Avoid switching encodings without a reason, because a conversion can alter characters if handled incorrectly.
If appearance or photos are part of the diary, retain the editable original and make a PDF/A export for convenient page-faithful reading. Keep image files alongside the entry and use filenames or notes that identify which entry they belong to. A PDF/A export is a companion, not a replacement for original editable files or separate photographs.
Make the archive resilient beyond the file format
The National Archives and Records Administration describes digital preservation as ongoing work aimed at keeping records usable while retaining qualities such as authenticity, accuracy, and functionality. Its Digital Preservation overview emphasizes continuing assessment and planning. For an individual, that translates into a repeatable routine rather than a one-time “save as” decision.
Keep at least two copies in different places. For example, keep one copy on your computer and another on a separate storage device or a trusted remote backup. Two folders on the same drive are still vulnerable to that drive failing. This is a practical adaptation of preservation planning; it is not a guarantee against loss.
Use clear folders and filenames. Organize entries by year and use consistent dates. Keep any README note with the archive explaining the file format, encoding, naming pattern, and which copy is the editable original.
Check the archive periodically. Open a few files from each year, check that special characters render properly, and confirm that the separate copies are present. If a file is damaged or unreadable, use another copy and replace the damaged one.
Refresh the storage as needed. When replacing a computer or storage device, copy the archive, then open files from the new location before retiring the old device. A file extension is not proof that the content transferred correctly.
The NDSA Levels of Digital Preservation is a framework created for practitioners to assess or build preservation programs. Its scope is more extensive than a personal diary, but it reinforces that preservation involves practices and storage, not just format selection. The steps above are deliberately scaled for an individual.
How to decide, in brief
If your diary is mostly words, choose UTF-8 plain text as the simplest long-term reading copy, and prioritize keeping redundant copies that you can verify. If layout is part of the diary’s meaning, keep the editable source and make a PDF/A companion. If entries contain photographs or other materials, keep those files with clear links to the relevant entry rather than assuming that a text or PDF file contains everything.
Whichever option you choose, test it with a handful of representative entries—including the longest entry and one with unusual characters or images—before using the format for all ten years. Reopen the files on a second device or application if possible. That small check helps reveal practical problems early; it cannot predict whether a format, device, or service will be available a decade from now.