Long-term archiving focuses on preserving digital information reliably for decades or centuries, prioritizing stability, accessibility, and independence from specific tools over efficiency. The "best" formats are mature, open standards with clear specifications, minimal dependencies, and widespread support. These formats contrast with proprietary formats tied to specific software or complex formats prone to obsolescence, reducing future access risks. Ideal candidates are simple, well-documented, and widely adopted for long-term preservation contexts.

Key examples include TIFF for master images in libraries and museums, valued for its lossless compression and metadata capabilities. PDF/A, a standardized subset of PDF designed explicitly for archiving, is heavily used for legal documents, contracts, and records management in government and finance due to its fixed layout and embedding requirements. Plain text (TXT) and CSV also serve as durable, simple formats for textual and tabular data.

Strengths of these formats include vendor neutrality, ensuring future readability without specific software licenses. Limitations often involve large file sizes (like uncompressed TIFF) or functional restrictions (PDF/A forbidding embedded executable code). Ethical implications center on guaranteeing access to cultural heritage and legal evidence. Future-proofing demands ongoing monitoring, possible migration to newer standards, and using integrity checksums, acknowledging that format selection is just one part of a robust preservation strategy.