General

Open vs Proprietary File Formats: Why It Matters

Published Mar 19, 2026 6 min read By ChangeThisFile Team

Quick Answer

Open file formats have publicly available specifications that anyone can implement without license fees. Proprietary formats are controlled by a single company, creating vendor lock-in and obsolescence risk. For long-term data access, interoperability, and tool ecosystem breadth, open formats are almost always the better choice.

When you save a file in PSD format, you're storing your work in a format controlled entirely by Adobe. If Adobe decides to change PSD, deprecate it, or stop supporting older versions, your files are at their mercy. When you save as PNG, you're using a format whose specification is published by the W3C, implemented by hundreds of independent tools, and controlled by no single company. Your files are yours.

The open-vs-proprietary distinction isn't academic purity — it has concrete consequences for data longevity, tool choice, interoperability, and cost. Governments and institutions increasingly mandate open formats for exactly these reasons. This guide explains the distinction, maps the landscape, and offers practical recommendations.

Defining Open and Proprietary Formats

Open format: The specification is publicly available, anyone can implement readers and writers without license fees, and no single entity controls the format's evolution. Examples: PNG, FLAC, EPUB, SVG, ODF, WebM, JSON, XML.

Proprietary format: The specification is not fully public, and/or implementation requires a license from the controlling company. Examples: PSD (Adobe), RAR (Alexander Roshal), KFX (Amazon Kindle), Pages/Numbers/Keynote (Apple).

Hybrid/ambiguous: Some formats occupy a gray area. DOCX is ISO-standardized (ISO/IEC 29500) but Microsoft's implementation includes undocumented extensions. H.265/HEVC has a published specification but requires patent license payments. RAR's decompression is documented (allowing readers) but its compression algorithm is proprietary (limiting writers).

Category	Open	Proprietary	Hybrid/Complex
Image	PNG, SVG, WebP, AVIF, TIFF, GIF, BMP	PSD, AI, CDR	HEIC (HEVC patents), JPEG XL (ISO but limited adoption)
Audio	FLAC, Opus, Vorbis, WAV, AIFF	WMA	AAC (ISO but patent-encumbered), MP3 (patents expired 2017)
Video	AV1, VP9, VP8, Theora, FFV1	ProRes (partially documented)	H.264 (ISO, widely licensed), H.265 (ISO, complex patents)
Document	ODF (ODT/ODS/ODP), PDF, Markdown, plain text	Pages, Numbers, Keynote	DOCX/XLSX/PPTX (ISO, but Microsoft-dominant)
Archive	ZIP, TAR, 7Z, gzip, bzip2, Zstandard	RAR (compression proprietary)	—
Ebook	EPUB	KFX (Kindle), iBooks	MOBI (documented but Amazon-controlled)
Data	JSON, XML, CSV, YAML, Parquet, Arrow	—	—

The Vendor Lock-In Problem

Vendor lock-in occurs when your data is stored in a format that only one tool fully supports, making it expensive or impossible to switch tools. This is the primary risk of proprietary formats.

Adobe PSD: PSD files with complex layer structures, smart objects, and adjustment layers can only be fully edited in Photoshop. GIMP, Affinity Photo, and other tools read PSD files but lose or misinterpret advanced features. If you've built a workflow around PSD layer effects and later want to switch from Photoshop, you'd need to manually reconstruct every file. Export to PNG for flat images, but you lose all editability.

Apple iWork: Pages, Numbers, and Keynote use Apple's proprietary formats. They work beautifully on macOS and iOS but are only partially readable on other platforms (through iCloud web apps). Sharing a Keynote presentation with a Windows colleague requires exporting to PPTX first.

Amazon Kindle: KFX and AZW3 formats can only be read on Kindle devices and apps. Your purchased ebook library is accessible only through Amazon's ecosystem. If Amazon changes terms or discontinues Kindle, your library is at risk. Convert AZW3 to EPUB for open-format copies (DRM-free files only).

Open Formats Build Better Ecosystems

When a format specification is public, developers can build tools without reverse-engineering or licensing negotiations. This creates a self-reinforcing ecosystem:

PNG has hundreds of implementations: libpng, stb_image, Pillow, ImageMagick, every browser engine, every OS image viewer. Bugs get found and fixed quickly because of the diversity of implementations.
FLAC has reference decoders, FFmpeg support, foobar2000, VLC, every smartphone OS, and streaming service support. The open spec means any device manufacturer can add FLAC support without license fees.
JSON has parsers in every programming language, built into most language standard libraries, used by virtually every web API. Its simplicity and openness made it the universal data interchange format.

Compare this to RAR: the compression algorithm is proprietary, so there's exactly one good RAR creator (WinRAR) and a handful of decompressors (mostly based on UnRAR, whose source Alexander Roshal publishes with restrictions). The tool ecosystem is thin because the format is controlled. Convert RAR to ZIP to escape this limitation.

Format Longevity and Company Risk

Companies go bankrupt, pivot, get acquired, or simply lose interest. When that happens, proprietary formats they controlled become orphaned.

Real examples of format orphaning:

Macromedia/Adobe Flash (SWF): Adobe killed Flash Player in 2020. Billions of SWF files became unplayable overnight.
Lotus 1-2-3 (.wk*): Lotus was the dominant spreadsheet in the 1980s. IBM acquired Lotus in 1995 and eventually discontinued the product. Opening .wk4 files today requires specialized legacy tools.
WordPerfect (.wpd): Once the dominant word processor. Corel still sells WordPerfect, but the format is barely supported outside their product. Converting old WPD files requires finding a copy of WordPerfect or a legacy converter.
Microsoft Works (.wps): Microsoft discontinued Works in 2007. The .wps format has no modern reader outside LibreOffice's limited import.

Open formats survive company changes because the specification is public. PNG (created by a committee, spec held by W3C), FLAC (created by Josh Coalson, now maintained by Xiph.org), and EPUB (created by IDPF, now maintained by W3C) all have governance structures that outlast any individual contributor or company.

Government and Institutional Mandates

Governments increasingly mandate open formats for public records, recognizing that taxpayer-funded data shouldn't be locked in proprietary formats:

European Union: The EU's interoperability framework recommends ODF (OpenDocument Format) for government documents. Several member states mandate ODF for public administration.
United Kingdom: The UK Government Digital Service mandates ODF for editable documents and PDF/A for non-editable documents in government.
India: The Indian government adopted ODF as the standard for electronic records in 2010.
United States: The Library of Congress recommends open formats (TIFF, WAV, PDF/A) for digital preservation. Federal courts require PDF/A for electronic filing.
NATO: STANAG 4609 specifies open formats for intelligence, surveillance, and reconnaissance data.

These mandates exist because governments realized that storing records in proprietary formats means taxpayers are perpetually paying license fees to access their own data, and format obsolescence means permanent loss of public records.

The Patent Problem: Open Spec, Restricted Implementation

Some formats have published specifications but require patent license fees to implement. This creates a middle ground that's neither fully open nor fully proprietary:

H.264/AVC: Specification is published by ITU/ISO. But implementing H.264 requires a license from MPEG LA's patent pool. The license is free for free internet video and relatively affordable for commercial use ($0.20 per unit above 100K, capped at $6.5M/year). Most companies just pay it, which is why H.264 is ubiquitous.

H.265/HEVC: Three competing patent pools (MPEG LA, HEVC Advance, Vantiva) with unclear and potentially overlapping claims. Total licensing cost: uncertain and possibly very high. This mess directly caused the formation of the Alliance for Open Media and the creation of AV1 as a royalty-free alternative.

AAC: ISO-standardized, widely implemented, but patent-encumbered through Dolby and Via Licensing. Patent fees are relatively low, which is why AAC became the standard for streaming music. But the patents prevent truly free implementations.

The lesson: an open specification is necessary but not sufficient for a truly open format. Royalty-free licensing (like AV1, VP9, Opus, and FLAC) provides the strongest guarantee of unfettered use.

Practical Format Recommendations

Use Case	Open Choice	Why
Photos (web)	AVIF, WebP, or PNG	AVIF is next-gen open; WebP for broad support
Photos (archival)	TIFF or PNG	Lossless, open, universally supported for decades
Documents (sharing)	PDF	ISO standard, renders identically everywhere
Documents (editing)	ODF (ODT/ODS/ODP) or DOCX	ODF is truly open; DOCX is ISO with caveats
Audio (archival)	FLAC	Lossless, royalty-free, widely supported. Convert from WAV
Audio (sharing)	Opus	Best quality per bitrate, royalty-free
Video	AV1 in MP4 or WebM	Royalty-free, matches HEVC quality
Ebooks	EPUB	Open standard, reflowable. Convert from MOBI
Archives	ZIP or 7Z	ZIP for compatibility, 7Z for better compression
Data interchange	JSON, CSV, or Parquet	Universal text formats or columnar binary

Choosing between open and proprietary formats is a decision about who controls your data. With an open format, you do — any tool can read and write it, any developer can build for it, and no company's business decisions can render your files inaccessible. With a proprietary format, you're renting access to your own data from a company that may not exist in 20 years.

There are legitimate reasons to use proprietary formats: PSD's layer editing is unmatched, and RAR's compression ratio for certain content types is excellent. But whenever an open alternative meets your needs — and it almost always does — use the open format. Your future self will thank you when the proprietary vendor pivots to AI and abandons their file format.

Key Takeaways

Open formats have public specs, royalty-free implementation, and no single controlling entity
Proprietary formats create vendor lock-in: your data depends on one company's continued existence and goodwill
Real formats have been orphaned when companies died: Lotus 1-2-3, WordPerfect, Flash — your data trapped with them
Governments increasingly mandate open formats to prevent taxpayer data lock-in
Patent-encumbered formats (H.265, AAC) are a middle ground: open spec but restricted implementation
For every proprietary format, a viable open alternative exists and is usually the better long-term choice

Frequently Asked Questions

Is DOCX truly an open format?

Partially. DOCX (Office Open XML) is ISO-standardized (ISO/IEC 29500), and the specification is publicly available. However, Microsoft's implementation includes undocumented behaviors, proprietary extensions, and features that other implementations struggle to replicate exactly. LibreOffice, Google Docs, and other tools can read and write DOCX, but complex documents often render differently. It's more open than DOC but less open than ODF.

Why does anyone use proprietary formats if open ones are better?

Three reasons: (1) Better tooling — Photoshop's PSD editing is genuinely superior to any open-format workflow for complex image editing. (2) Ecosystem lock-in — if everyone in your industry uses PSD, switching has coordination costs. (3) Platform defaults — Apple devices save to HEIC by default, Amazon sells Kindle books in KFX by default. Users follow defaults without choosing consciously.

Are open formats always free to use?

Open specification doesn't always mean royalty-free. H.264's spec is public (ISO standard) but implementing it requires patent license fees. Truly free formats (PNG, FLAC, AV1, Opus, WebM) are both open-spec and royalty-free. When evaluating a format's openness, check both the specification access and the patent/licensing situation.

Can I convert all my files from proprietary to open formats?

For most file types, yes. PSD to PNG/TIFF (loses layers but preserves the image). RAR to ZIP or 7Z. MOBI to EPUB. WMA to FLAC or Opus. DOC to DOCX or ODF. The main exception is DRM-protected content — DRM-locked files can't be converted without first removing the DRM, which may have legal restrictions depending on jurisdiction.

What happened to companies that relied on proprietary formats?

Mixed outcomes. Adobe thrived by making PDF an open ISO standard while keeping PSD proprietary — the open format drove platform adoption, the proprietary format drove tool sales. Microsoft standardized DOCX (sort of) under competitive pressure from ODF. Companies that held too tightly to proprietary formats often lost market share as open alternatives gained traction — the GIF/LZW patent enforcement directly created PNG and accelerated GIF's decline for still images.

Is RAR really proprietary if there are tools that can open it?

Yes. Alexander Roshal publishes the UnRAR source code for decompression, but with restrictions: you can build a RAR reader but not a competing RAR creator. The compression algorithm itself is proprietary. This means RAR has many readers (7-Zip, WinRAR, The Unarchiver) but effectively one writer (WinRAR). Compare to ZIP where dozens of tools can both create and extract archives. RAR's decompression availability prevents total lock-in but doesn't make it open.

Do open formats have worse features than proprietary ones?

Sometimes, but the gap is narrowing. PSD's layer editing capabilities genuinely exceed what PNG or TIFF can represent. ProRes video has features specific to Apple's professional workflow. But in most categories, open formats match or exceed proprietary ones: FLAC matches any proprietary lossless audio codec, AV1 matches or beats H.265, EPUB matches or exceeds KFX for most ebook use cases, and PNG/AVIF handle everything PSD can for final-output images.

Should businesses mandate open formats internally?

For document exchange and archival, yes — mandating PDF for distribution and ODF or DOCX for editable documents prevents tool lock-in. For creative work, it's harder — forcing designers off PSD or video editors off ProRes has productivity costs. The pragmatic approach: use open formats for interchange and archival, allow proprietary formats for specialized creative tools, and always maintain an export path to open formats.

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