Practical answers to the questions people ask before converting a file — and the tool that handles each one.
Use JPG for photographs, where its compression makes files several times smaller with no difference you can see. Use PNG for screenshots, logos, diagrams and anything with text, sharp edges or a transparent background, where JPG's compression leaves smudges. If the image is for a website, WebP usually beats both.
Read the guideFor most websites, WebP is the best default: roughly 25–35% smaller than JPG, with transparency like PNG, and supported by every current browser. AVIF can be smaller still but is slower to create. Use SVG for logos and icons, and keep JPG or PNG only where something outside the browser needs them.
Read the guideHEIC is the format iPhones have used for photos since iOS 11 in 2017. It stores the same picture in roughly half the space of a JPG, but many Windows PCs, websites and apps still cannot open it. Convert HEIC to JPG when you need to share or upload a photo, or set Camera → Formats → Most Compatible so new photos are saved as JPG.
Read the guidePhone photos usually carry EXIF metadata: the exact GPS location, the date and time, and the camera and phone model. Big social networks strip it when they publish a photo, but email, cloud links, messaging apps sending files and many websites pass it on intact. Remove it before sharing, or turn off location tagging in your camera settings.
Read the guideA large PDF is almost always large because of the images inside it — scans or photographs at full resolution. Compressing those images, while leaving the text as real text, shrank colour scans by 39–86% in our tests. Black-and-white scans and PDFs that are mostly text are already compact and barely change; split those instead if they are still too big.
Read the guideIt depends on what kind of PDF it is, not on how big it is. In our test of 14 public-domain documents, colour scans shrank by 39–86% at the default Balanced level and by up to 98% at Strong. Black-and-white scans, long text documents and e-books from professional publishing software barely changed. Every compressed file kept every page, and its text read back exactly as before.
Read the guideYou do not need to print, sign and scan. Open the PDF in an online editor, draw your signature with a mouse or finger (or type or upload it), place it on the page, add the date, and save. This kind of electronic signature is accepted for most everyday agreements in the UK, EU and US, though some documents, such as wills and deeds, have stricter rules.
Read the guideTo protect a PDF, encrypt it with a password: without the password the contents cannot be read at all. Use AES-256 encryption, which every current PDF reader supports, and a long password shared separately from the file. Print and copy restrictions are honoured by readers but are not real security. To remove a password you know, unlock the PDF and save an unprotected copy.
Read the guideSend a PDF when the document is finished and must look identical for everyone — CVs, contracts, invoices, applications. Send a Word document when someone needs to edit it. Word to PDF converts faithfully; PDF to Word is a reconstruction, which works well for simple documents and needs tidying for complex layouts.
Read the guideUse 128 kbps for speech, podcasts and lectures; 192 kbps for most music, which most people cannot tell from the original; and 320 kbps when converting from a lossless source such as WAV or FLAC and file size does not matter. Converting a low-bitrate file to a higher bitrate adds size but no quality.
Read the guideMP4, MOV and AVI are containers: boxes that hold video and audio encoded with a codec. MP4 with H.264 video and AAC audio plays on virtually every phone, browser, TV and upload form, so it is the format to share in. MOV is Apple's format and plays best on Apple devices; AVI is a 1990s Windows format that modern players often refuse. Converting either to MP4 usually fixes playback problems.
Read the guideUse JPG for photographs, where its compression is efficient and the quality loss is invisible. Use PNG for logos, screenshots, diagrams and anything with text or transparency, where sharp edges matter more than file size.
Almost certainly yes. WebP produces files 25–35% smaller than JPG at the same visual quality, supports transparency like PNG, and is supported by every current browser. It is the single easiest image win for page speed.
Apple made HEIC the default in iOS 11 because it halves the storage each photo needs. Support outside Apple devices is still patchy, so convert to JPG when sharing — or switch your camera to ‘Most Compatible’ in Settings.
It depends entirely on the document. PDFs record where marks sit on a page rather than the structure behind them, so simple single-column text converts cleanly while multi-column and heavily designed layouts need tidying afterwards.
150 DPI for anything viewed on a screen, 300 DPI if it will be printed, and 72 DPI for small thumbnails. Higher settings produce sharper images but grow the file size quickly with no visible benefit on screen.
128 kbps is fine for speech and podcasts. 192 kbps suits most music and is a sensible default. 320 kbps is worth it only when converting from a lossless source such as FLAC and storage is not a concern.
GIF is a 1987 format with no modern compression — it stores frames almost independently and is limited to 256 colours. Keeping clips under ten seconds and reducing width and frame rate are the effective ways to control size.
Both are containers that can hold codecs modern players no longer ship. Converting to MP4 with standard H.264 video produces a file that plays on essentially every device, browser and upload form.