An arrow beats a circle
Most people reach for a circle. An arrow is usually clearer and the reason is direction.
A circle says "somewhere in here". That works when the thing you are marking has an obvious boundary, like a bolt or a switch. It works badly when it does not: a circle drawn on a metre of wall tells the reader that something in that metre is wrong, and leaves them to guess what.
An arrow points. It comes in from outside the subject, so it does not cover the thing it is identifying, and it survives being made small far better than a thin circle does.
Boxes sit between the two. They are the right choice for regions rather than points: a section of drawing, a paragraph in a screenshot, one panel of four.
Draw thicker than feels right
Annotation is almost never viewed at the size it was drawn at.
Photographs go through messaging apps that recompress them, email clients that resize them, and documents that scale them down to fit a page. Each step softens fine lines, and a delicate one-pixel arrow can be more or less erased by the time it arrives.
A mark that looks slightly heavy-handed on your screen at full size is usually the one that is still legible after the image has been through three pieces of software. Err towards crude.
Pick a colour that is not in the photograph
Red is the reflex and it is frequently the worst available choice.
Brickwork, rust, timber, warning signage, hazard tape, hi-vis, soil and a great deal of machinery are all red or close to it. A red arrow on any of those is an arrow you have to hunt for.
Bright green, magenta and cyan are uncommon in most real photographs, which is precisely why they work. Look at the mark against the actual background before deciding, rather than picking the colour you always pick.
Marks are permanent, and that is the point
The shapes are drawn into the pixels rather than kept as a separate layer. Once exported, there is nothing to select, move or delete.
For annotation that is the correct behaviour. If you are marking a defect, a discrepancy or something you want a record of, you do not want the file to arrive with your arrow sitting on a layer somebody can nudge or switch off.
The cost is that you cannot revise it either, so keep the original photograph. Nothing here overwrites it, and the download is a separate file.
Check the background before you send it
When you are concentrating on marking a problem it is easy to miss what else is in the frame.
Photographs taken on site routinely include a face, a number plate, a delivery note on a bench, a name on a helmet, a screen with something on it, or an address on a package. Once the image is attached to an email it is out of your hands.
Have a look at the whole frame, not just the part you have annotated. There is a blur tool on this site for the bits that should not go out, and it bakes the blur in rather than layering it on top where somebody could peel it off.
Opened, marked up and saved without leaving the tab
The image is opened, marked up and saved entirely in your browser. No account, no upload, no queue, and no watermark on the way out.
Common questions
What is the clearest way to point at something in a photo?
An arrow, from outside the subject, pointing in. It beats a circle because it has a direction, and it beats a highlight because it survives being made small. Circles are fine when the thing you are marking has a clear boundary; they fail when it does not, because a circle round half a wall tells the reader very little.
Why do my annotations disappear when I send the photo?
Usually because they were too thin. Messaging apps and email clients recompress and resize images heavily, and a one-pixel line or a small arrow can be almost erased by that. Draw thicker than feels necessary: a mark that looks slightly crude at full size is the one that still reads after the image has been through three apps.
What colour should I use?
One that is not in the photo. Red is the default and is a poor choice on brickwork, rust, warning signs and anything on a construction site. Bright green, magenta and cyan are rare in most photographs, which is exactly what makes them visible. Check the mark against the actual background rather than choosing out of habit.
Can I remove or edit a mark after saving?
Not from the saved file. The shapes are drawn into the pixels, so an exported JPEG or PNG has no separate layer to move or delete. That is deliberate for annotation, since it means nobody receiving it can quietly shift your arrow, but it does mean you should keep the original photo.
Should I blur anything before sending it?
Often, yes, and it is easy to forget when you are focused on marking a defect. A photograph taken on a job can contain a face, a number plate, a document on a desk or a name badge in the background. There is a blur tool on this site that bakes the blur into the pixels rather than layering it on top.
Is the picture sent away to be drawn on?
No. Everything happens in your browser and nothing is sent to a server. No account, no queue, and no size limit beyond your own device.