What an image metadata editor writes
A photograph carries a small record beside the pixels: who made it, what it shows, when it was taken, and sometimes where. Export buttons keep the picture and drop the words. You can add metadata to an image here after that export, using the fields a catalog expects.
Title is the short name. Description is the longer caption. Keywords are the terms you would search later. Author is the credit. Copyright is the rights line that should travel with the file. Date is the calendar day you want recorded. Latitude, longitude, and an optional altitude add GPS location to a photo when the camera missed the pin. Leave a box blank and that part of the file stays as it was. Clear a box that already has a value and that value is removed. Camera make, lens, exposure, orientation, and the color profile are copied through.
Three standard records for the same facts
Programs do not share one notebook, so the same facts are written into each record the file can hold. EXIF is the camera record, and it is what phones open first. You can add EXIF data for the description, author, copyright, date, and GPS without touching shutter speed or the lens name. IPTC is the older press record. Captions, bylines, and IPTC keywords are what many news systems still index. XMP metadata is the XML record. It holds the title, caption, creator, and rights, and it is also where a private field can sit without pretending to be a camera tag.
JPEG can carry all three while the compressed scan is copied unchanged. PNG stores the camera record in an eXIf chunk and the XML in a text chunk. WebP uses the same idea, and a simple WebP file is wrapped so those chunks have a legal place. TIFF is already the camera container, so tags are updated in the directory and the picture strips stay where they were. AVIF keeps the two records as separate items and points them at the picture. An image metadata editor that only filled one of those records would leave the other programs blind.
If the file already has an XML packet this page can merge, new values replace only the fields you changed. A damaged packet is left untouched, and the camera and press fields are still updated.
Custom tags
Standard fields do not cover a job number, a client, or a shoot code. Custom tags are that extra layer: a name and a plain-text value. The name starts with a letter and may use letters, numbers, underscore, or hyphen, so it cannot smuggle markup. On every format the pairs live in one private XML namespace. PNG also writes each pair as its own text chunk, which is the usual non-standard place in that format. Twenty pairs is the limit. Remove a row and download again to delete that pair. Using an image metadata editor this way keeps your archive notes on the file without inventing fake camera tags.
Files you can save
JPG receives the camera block, the press block, and the XML packet. PNG receives the camera block, the XML packet, and custom text. WebP, lossy or lossless, receives the camera block and the XML packet. Normal TIFF is accepted. BigTIFF is refused. AVIF is accepted when it has one media-data box and a picture location this page can recalculate. Fragmented AVIF is refused rather than rewritten into a file a browser cannot open. The type comes from the first bytes, not the extension, so a renamed SVG is rejected. Declared sides over 100,000 pixels are rejected. The limit is 50 MB.
Quality, privacy, and search
Saving a JPEG through a canvas quantizes it again. This page splices the new record around the existing compressed data, so the picture payload matches before and after. That matters for a print master and for a web image you already sized. An image metadata editor is the wrong place to shrink the file. Compress later only with a tool that keeps the record you just wrote.
The form is not posted anywhere. The script reads the file in memory and builds the download in the browser, so a client name in a custom tag never lands on a host.
Keywords inside a file do not rank a page by themselves. Google Images can show the creator and the copyright stored in the picture, which is a sound reason to add copyright to a photo before you publish, and the description is a useful caption for anyone who saves the file later. Ranking still depends on the page around the image: visible text, alt text, and the file name. Another pass with an image metadata editor will not change that. It only keeps the label with the file.
To strip the camera record and the location before a public post, use the EXIF remover. One tool writes the label you want to keep. The other removes the label you do not want to share.