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.SW file extension

To open .SW files on Windows, identify the file type: if it opens as readable text with protein annotations/records, treat it as UniProt/Swiss-Prot; if it sounds like audio or comes from an audio workflow, treat it as raw PCM audio.

To open a .sw file, determine whether it is a UniProt/Swiss-Prot (UniProtKB) flat-file record (text-based protein data) or a raw signed 16-bit PCM audio file. Swiss-Prot-style .sw files can be read with bioinformatics tools such as Biopython’s SwissProt/“swiss” parser, while audio .sw files need an audio editor/player that can import raw PCM with the correct settings.

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Last updated: June 11, 2026 · Reviewed by Julian Stricker

What “reviewed” means on this page
  • Format fit: whether the “what is this file?” description matches common real-world use of the extension, including category, typical MIME types, and aliases.
  • Opening paths: whether Windows / macOS / Linux steps read plausibly for current OS dialogs and default apps; we remove fantasy menus and unsafe shortcuts.
  • Security framing: whether risk notes match the extension class (for example executables vs plain data) and whether affiliate wording does not contradict the security section.
  • Sources and further reading: whether external links point to vendors, standards bodies, or other primary references where possible; we avoid inventing details we cannot ground.
  • Limits: this is clarity and safety-messaging QA, not a guarantee that every statement is exhaustive or that every binary you download is harmless.

Full methodology in the Imprint — The Imprint also states where AI is used and what that does—and does not—replace.

Open on your device

Choose your operating system for a dedicated step-by-step opening guide.

How to open .SW files

Use these platform-specific instructions to open .SW files safely.

Windows

  1. Identify the file type: if it opens as readable text with protein annotations/records, treat it as UniProt/Swiss-Prot; if it sounds like audio or comes from an audio workflow, treat it as raw PCM audio.
  2. For Swiss-Prot/UniProt flat files: open in a text editor for viewing, or parse it with a bioinformatics toolkit such as Biopython (format name commonly referred to as “swiss”).
  3. For raw PCM audio: use an audio tool that supports importing “Raw” data and manually set signed 16-bit PCM plus the correct sample rate and channels.
Full Windows guide

Mac

  1. Check whether the file is text (UniProt/Swiss-Prot flat file) by opening it in a text editor; if it is binary/noisy audio data, treat it as raw PCM audio.
  2. For Swiss-Prot/UniProt flat files: view in a text editor or process with a scripting environment using Biopython’s SwissProt/“swiss” parsing support.
  3. For raw PCM audio: import it as raw audio in an editor/player that supports raw PCM and provide the correct parameters (signed 16-bit, sample rate, channels).
Full Mac guide

Linux

  1. If your desktop labels .sw as chemical/x-swissprot, try opening it in a text editor first to confirm it is a UniProt/Swiss-Prot flat file; otherwise treat it as raw audio.
  2. For Swiss-Prot/UniProt flat files: process with Biopython (SwissProt/“swiss”) or other bioinformatics tools; viewing is possible in any text editor.
  3. For raw PCM audio: import as “raw” PCM in an audio application and manually set signed 16-bit plus sample rate/channels (raw audio has no header to auto-detect).
Full Linux guide

iOS

  1. iOS generally will not reliably recognize or preview .sw; transfer the file to a desktop to inspect whether it is UniProt/Swiss-Prot text data or raw PCM audio, then open it with appropriate desktop tools.
Full iOS guide

Android

  1. Android typically won’t identify .sw correctly; move the file to a desktop to determine whether it is UniProt/Swiss-Prot flat-file text or raw PCM audio and open it with suitable tools (text editor/bio tools vs. raw audio import).
Full Android guide

Security notes

  • Swiss-Prot/UniProt flat files are plain text data, but treat them as untrusted input for scripts and parsers: a malformed file can trigger bugs or excessive resource use in downstream tooling (e.g., parsers).
  • Do not rename .sw to another extension to force an app to open it; this can lead you to use the wrong parser/import mode and mis-handle the data (especially for raw audio, where import settings matter).
  • If you obtained a .sw from an unknown source and it is not readable text, be cautious: the extension alone does not guarantee it is only data (it could be arbitrary binary content). Prefer inspecting it safely (read-only) before processing.

If you did not expect this file

This extension is usually plain data, text, or structured content—not a program by itself. The practical risk is social engineering (a scam attachment or misleading filename). For trusted senders you rarely need heavy-handed antivirus wording; use these tools when you want an extra check on unexpected downloads.

Avast

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Can't open this file?

These are the most common causes and fixes when .SW files fail to open.

Common reasons

  • The .sw file opens as “unknown” or with the wrong app
  • Raw .sw audio plays as noise or at the wrong speed
  • Bioinformatics parser fails or stops mid-file
  • Linux shows MIME type chemical/x-swissprot but the file is not UniProt data

Fix steps

  1. Open a copy in a plain text editor: UniProt/Swiss-Prot flat files are readable text records; raw PCM audio will not look like structured text.
  2. If it is Swiss-Prot/UniProt text, process it with a UniProt-aware parser such as Biopython’s SwissProt/“swiss” support; if it is audio, import it as raw PCM in an audio tool and set parameters manually.

OS-specific troubleshooting

What is a .SW file?

In bioinformatics workflows, “Swiss-Prot/TrEMBL flat file” refers to UniProtKB’s text-based distribution format for protein sequence and annotation data. Separately, the .sw extension is also used for raw signed 16-bit PCM audio (a headerless audio stream), which requires the correct sample rate/channels to play properly. On Linux, some systems may map .sw to the MIME type chemical/x-swissprot via the shared MIME-info database mechanism.

Background

UniProt distributes protein data in several formats, including the Swiss-Prot/TrEMBL (UniProtKB) flat file, which is a plain-text, line-oriented record format designed for robust exchange of sequence and annotation information. UniProt’s technical documentation points to the UniProtKB flat file format manual, which is the authoritative reference for fields, tags, and structure.

For practical use, Swiss-Prot-style files are often processed programmatically rather than “opened” in a single dedicated desktop app. Biopython includes a reader for the SwissProt/UniProt flat-file format (via its SwissIO/SeqIO support), which is a common option for parsing and converting records in research pipelines.

However, .sw is not exclusive to UniProt data. File extension references also document .sw as raw signed 16-bit PCM audio. Because raw PCM has no header, software cannot reliably auto-detect playback parameters; you must know (or guess) settings like sample rate, bit depth, and channel count.

On Linux desktops, file-type detection and default app associations can be influenced by the freedesktop.org shared-mime-info database and its specification, which define how extensions (globs) can map to MIME types. This explains why some environments may label .sw as a Swiss-Prot-related data type even when your specific file is not.

Common MIME types: chemical/x-swissprot

Further reading

Authoritative resources for more details on the .SW format.

Common .SW issues

The .sw file opens as “unknown” or with the wrong app

The .sw extension is ambiguous (Swiss-Prot/UniProt data vs raw PCM audio), and OS file associations may map it to a Swiss-Prot MIME type even when the content is different.

  1. Open a copy in a plain text editor: UniProt/Swiss-Prot flat files are readable text records; raw PCM audio will not look like structured text.
  2. If it is Swiss-Prot/UniProt text, process it with a UniProt-aware parser such as Biopython’s SwissProt/“swiss” support; if it is audio, import it as raw PCM in an audio tool and set parameters manually.

Raw .sw audio plays as noise or at the wrong speed

Raw PCM has no header, so the player cannot know the sample rate, number of channels, or exact encoding; incorrect settings produce noise, distortion, or wrong playback speed.

  1. Re-import the file as raw audio and confirm it is signed 16-bit PCM (as documented for .sw audio).
  2. Try the correct sample rate/channels from the source workflow; if unknown, test common sample rates (e.g., 44100 or 48000 Hz) and mono vs stereo until it sounds right.

Bioinformatics parser fails or stops mid-file

Swiss-Prot/UniProt flat files are structured records; truncation or non-conformant formatting can cause parsers to error.

  1. Verify the download/transfer completed and the file is not truncated.
  2. Validate against UniProt’s flat file format documentation and re-export/re-download from the original source if possible.

Linux shows MIME type chemical/x-swissprot but the file is not UniProt data

On Linux, shared-mime-info can associate extensions with MIME types using installed rules; this is extension-based and may not reflect the actual content.

  1. Inspect the file content (text vs binary) rather than relying on the MIME label alone.
  2. If needed, open it with an app that lets you explicitly choose “import raw audio” or “open as text,” depending on what the file actually contains.

FAQ

What does a .sw file usually contain?

Most commonly it refers either to UniProt/Swiss-Prot (UniProtKB) flat-file protein data (text-based) or to a raw signed 16-bit PCM audio file. The same extension can be used for different purposes, so check the content/source.

How can I tell if my .sw is Swiss-Prot/UniProt data?

Try opening it in a plain text editor. Swiss-Prot/UniProt flat files are readable, structured text records described in UniProt documentation; raw audio will not appear as meaningful text.

Can I convert a Swiss-Prot/UniProt flat file with Biopython?

Yes. Biopython includes support for parsing the SwissProt/UniProt flat-file format (often referred to as “swiss”), which you can use to read records and then export to other sequence formats supported by Biopython.

Why can’t my phone open a .sw file?

Mobile platforms typically lack built-in viewers for UniProt flat files and do not reliably import headerless raw PCM audio. It is usually easiest to transfer the file to a desktop system to identify the type and open it with appropriate tools.

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