JPG files use lossy compression optimized for photographs, yielding small file sizes while holding visual accuracy.
Common Uses
Sharing photographs online and via email
Displaying images on websites
Storing digital photos at speed
JPG Optimization FAQ
What is a JPG file?
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JPG (JPEG) is an image format that uses lossy compression, ideal for photographs and complex images.
Is a JPG the same thing as a JPEG?
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The same thing exactly: one standard, one bitstream, two spellings. The three-letter extension exists because early DOS filenames allowed only three characters, and the four-letter one is the original. Renaming a file from one to the other converts nothing and degrades nothing, and every camera, browser and editor reads both. The only thing that ever differs is software fussy enough to judge a file by its extension. JPG is the JPEG standard from 1992, served under the .jpg, .jpeg and .jfif extensions alike, and after three decades it is still the format most cameras and most websites use for photographs.
Does re-saving a JPG make it worse every time?
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Yes, and that is the one thing worth knowing about the format. Each save re-runs the lossy encoder over an image that has already been through it, so artefacts compound — visible as blocking around text and haloes on hard edges after a handful of generations. Edit from a lossless master and export to JPG once, at the end, rather than repeatedly opening and re-saving the same file. JPG is lossy: the image is transformed with a DCT, quantised, and entropy-coded, with a quality knob controlling how much is discarded.
Why does every camera and phone hand me a JPG?
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Because it is the format the whole photographic chain settled on decades ago, and nothing since has been worth the compatibility risk to a camera maker. The sensor data is processed and encoded in the camera itself, at a quality setting buried in a menu, and what lands on the card is already a finished picture. That is why the first conversion of a photograph is never the lossy step people worry about — the lossy step already happened, inside the camera.
What quality setting should I use when converting to JPG?
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Somewhere between 80 and 90 for anything a person will look at. Below about 75 the artefacts start to show on skin, sky and any large flat area; above 95 the file grows quickly while almost nobody can see the difference. The setting is not a property of the image, it is a decision about this particular export — so choose it for where the file is going, and keep the original for the next time you need a different answer.
Why did my transparent background turn white in the JPG?
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Because JPG has no alpha channel to keep it in. Every pixel has to be a solid colour, so transparency is composited against a background — white by default — the moment the file is written. Nothing is recoverable afterwards. If the image needs to sit on a coloured page or over a photograph, convert to a format that stores transparency instead. JPG has no transparency, degrades further every time it is re-saved, and produces visible blocking on flat colour and sharp text.
Can JPG hold CMYK colour for print?
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It can, which is why files from print workflows sometimes look strange on screen: the colours are specified in ink percentages for a press rather than in light for a monitor. Most web-facing formats are RGB only, so a conversion has to translate, and the translation is approximate — saturated cyan and orange shift most. For anything heading to a printer, keep the original alongside whatever you convert.
Does it matter that JPG is over thirty years old?
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Age itself is not the problem — several formats from that era are still perfectly good, precisely because everything has had decades to implement them. What matters is what the era assumed: small files, modest processors, no network, and features nobody needed yet. Where those assumptions still fit, the format is fine. Where they do not, that is the reason to convert.
Is camera and location metadata kept when I convert a JPG?
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It is carried across where the target format supports it — camera model, exposure, capture time, and GPS coordinates if the device recorded them. That last one is worth a thought before publishing: a photo straight off a phone can carry the exact location it was taken. Strip the metadata during conversion when the image is going somewhere public.
Can I use JPG directly on a web page?
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Yes — every current browser renders it natively, so it needs no fallback copy and no conversion at publish time. The remaining question is weight rather than support: the same picture in a modern web format is frequently a third of the size at the same visible quality, which is worth doing on anything that appears above the fold. JPG compresses natural photographs superbly and is readable by literally every device, browser and printer in existence.
Can I just rename the extension instead of converting JPG?
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Almost never, and it is worth understanding why: the extension is a label, while the bytes inside are structured for one specific format. Renaming produces a file whose name promises something its contents do not deliver, and whatever opens it either refuses the file or misreads it. The one narrow exception is two formats that are genuinely the same container under different names — and even then a proper rewrap is safer than a rename.
Can I convert a whole folder of JPG files in one go?
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With an account, yes — drop them in together and they are queued as one job rather than handled one at a time, with the same settings applied across the batch and the results returned together. Free conversions run a single file at a time (merge tools take two); a paid plan is what unlocks batch processing and the larger per-file limit, which is what makes converting a whole archive practical.
