Choosing the right file format: a practical guide

“Which format should I use?” is the wrong question, because the answer depends entirely on what you are going to do with the file. A format is a trade-off between size, quality, compatibility, and editability — and the right trade-off changes with the task. This guide skips the exhaustive spec sheet and gives you working defaults, by job.

For photos

• JPG — the compatibility default. Small, supported everywhere, but lossy: every save discards a little data. Right for photos you are sharing or uploading.
• PNG — lossless and supports transparency. Bigger. Right for screenshots, logos, and anything with sharp edges or text.
• WebP — smaller than JPG or PNG at the same quality, and now widely supported. The modern default for web images.

Rule: share in JPG or WebP; keep the original untouched.

For documents

• PDF — the “it will look the same on every screen” format. Fixed layout, universal. Right for sending, publishing, and archiving a finished document.
• DOCX — editable, with tracked changes and styles. Right while you are still working on the document.
• Markdown — plain text with light structure. The most portable, and the best base for converting to other formats later.

Rule: edit in DOCX or Markdown, finish in PDF.

For audio and video

• MP3 — the compatibility default for audio. Lossy, but small and universal.
• MP4 — the compatibility default for video. Widely supported, reasonable quality.
• Lossless / source formats — keep them while you are editing; only compress for the final delivery.

Rule: edit from the highest-quality source you have; compress only at the end.

For archives

• ZIP — the universal default. Compresses many small files well, and it is lossless: your files come back exactly.
• 7z / RAR — better compression ratios, but less universal support.

Rule: ZIP for anything you need to send; 7z when you are storing locally and size matters more than compatibility.

The three questions that settle it

When you are unsure, ask the file three questions:

1. Who is it for? A format you send to someone should be one they can open without effort. When in doubt, go with the most universal option.
2. Will it be edited again? If yes, use an editable or lossless format and protect the original. If no, optimize for size and compatibility.
3. Does it need to look or sound exactly right? If the layout or the final pixels matter, use a fixed or lossless format. If it is a working copy, optimize for speed.

A naming habit that saves you later

Format choice is only half the problem; the other half is remembering why you chose it. A light naming convention removes the guesswork when you come back to a file in six months:

• Keep the original’s name and extension intact — do not rename a scan.png to scan.jpg.
• Add a short tag when the file is a copy made for a purpose: contract-2026.pdf for the final, contract-2026-draft.docx for the editable working copy.
• For archives, put the date and what is inside in the name: invoices-2026-03.zip.

A file you can read without opening it is a file you can find, and a file you can find is a file you will not accidentally re-download or re-convert.

The one-sentence summary

Pick the format for the job it has to do: universal for what you send, editable or lossless for what you still touch, fixed or lossless for what has to stay exact — and name it so that future you does not have to remember any of this.