File Formats Explained: Which One for Which Job?
Saving a file in the wrong format can mean fuzzy logos, huge email attachments or documents that look different on someone else’s computer. Understanding a few categories of format removes most of the guesswork. This guide sticks to general principles, since software support changes over time.
Raster versus vector
Raster images are made of a grid of pixels. They suit photographs and detailed artwork but lose sharpness when enlarged. Vector images are described by mathematical shapes and lines, so they can scale to any size without blurring. Logos, icons and simple illustrations are usually best kept as vectors, with raster exports made for specific uses.
Common image formats
| Format type | Typical strengths | Typical caution |
|---|---|---|
| JPEG | Small files for photographs | Lossy compression; repeated saving degrades quality; no transparency |
| PNG | Sharp edges, text and transparency | Photographs can create large files |
| GIF | Simple animations, limited colours | Poor for photos; files can be heavy |
| SVG | Scalable logos and icons on the web | Needs checking for compatibility in some applications |
| WebP and similar modern formats | Efficient files for web use | Older software may not open them |
| TIFF | High-quality archiving and print workflows | Large files |
Documents
- PDF keeps layout fixed across devices, making it suited to sharing finished documents, forms and print files.
- Editable word-processor files suit drafts that others must change.
- Plain text and similar simple formats are durable and light, but carry no styling.
- Spreadsheet files hold structured data and formulas; exported plain-text tables are handy for moving data between systems.
Audio and video
Containers and codecs are different things: the container is the wrapper, and the codec is the method used to compress the sound or picture inside. Widely supported choices make sharing easier, whereas niche combinations can fail on certain devices. For editing, keep original, less-compressed files; export compressed versions for distribution.
Compression: lossy and lossless
Lossy methods discard information to reduce size, and the loss cannot be reversed. Lossless methods shrink files without discarding anything. Keep a lossless or original master of important work and make lossy copies as needed.
Resolution and size
- For screens, match image dimensions to how large they will appear, rather than uploading something far bigger.
- For print, higher resolution is needed because printed detail is finer; confirm requirements with your printer.
- Check colour mode expectations: screen work generally uses one system while print workflows often use another.
Practical habits
- Name files clearly, with dates or version numbers, and avoid spaces or unusual characters for web use.
- Keep source files, such as layered designs, separately from exports.
- Check metadata before sharing; photos can contain location details.
- When unsure what the recipient needs, ask. A one-line question saves a round of revisions.
As a rule of thumb, keep an editable master, export for the destination, and test the result on the device where it will be seen.
Archiving for the long term
If you need files to be readable many years from now, favour widely documented, non-proprietary formats and keep more than one copy in separate places. Revisit them occasionally, since storage media age and software support changes. A simple yearly check of your most valuable files is usually enough to catch trouble early, while there is still time to convert them.