Circle what to change.Give AI the exact coordinates.
01 / Select · Copy
Circle the area. Show your agent what to change.
These stray lines beside the collar.
● ● ●
Illustration edit
Original image already shared
Continue editing the image
Message your agent…
{"mask_spec_version":"1.0","instruction":"This JSON identifies areas the user selected in the source image. Interpret the selected areas and prompt in the context of the current conversation.","source_image":{"file_name":"original.png","width":1536,"height":1024},"coordinate_system":{"origin":"top-left","x_direction":"right","y_direction":"down"},"regions":[{"id":1,"shape":"polygon","points_px":[[536,609],[594,628],[609,701],[563,722],[532,678]],"points_normalized":[[0.34896,0.59473],[0.38672,0.61328],[0.39648,0.68457],[0.36654,0.70508],[0.34635,0.66211]]}],"prompt":"Remove the selected stray lines and refine the edge between the hair and collar."}
Send ↑
AGENT
Editing the selected area…
edited-image.pngLocal edit complete
1 selection
Copy JSON
Area and instructions copied
Before
After
‹ ›
01 / 03 Scroll down to select a detail
Illustrative demo
Skip demo ↓
How it works
Three steps. Done in seconds.
01
1. Drop in your image
Drop in a PNG, JPEG/JPG or WebP image, or click Open Image.
02
2. Circle the spot
Drag to draw an outline, then adjust the region or its nodes. Select multiple areas when needed.
03
3. Copy JSON to your agent
Copy the data and send it with the original image to your agent. Add your instructions when needed.
Need pixel-level precision?Export a black-and-white PNG when you need a mask: white selections on a black background, at the original image dimensions.
Why Flash Mask
Why Flash Mask
/ 01
Show exactly where to edit
Send the selected area and your instructions to your agent, without explaining “over here” or “next to that”.
/ 02
Quick selections, ready to share
Draw an outline and copy the coordinates. Need a mask? Export a black-and-white PNG at the original image size.
/ 03
Open the page and start
Start in Chrome or Safari on your computer, with no installation or account.
Private by design
Your images stay on your device.
Images and editing data stay local, with no uploads or access by advertisers. The Mac app works offline.
Buy once. No subscription.
Flash Mask
Mac App
$3.99
$5.99Launch offer
Unlimited useNo adsWorks offline
All 1.x updates included
Web version
Use for free
3 tasks on day one, then 1 daily. Watch an ad when you need more.
Mac App: macOS 26 or later · Apple SiliconPrices vary by App Store region.
Circle what to change.Give AI the exact coordinates.
Circle an area to get JSON for your agent or a black-and-white mask.
01 / Select · Copy
Circle the area. Show your agent what to change.
These stray lines beside the collar.
● ● ●
Illustration edit
Original image already shared
Continue editing the image
Message your agent…
{"mask_spec_version":"1.0","instruction":"This JSON identifies areas the user selected in the source image. Interpret the selected areas and prompt in the context of the current conversation.","source_image":{"file_name":"original.png","width":1536,"height":1024},"coordinate_system":{"origin":"top-left","x_direction":"right","y_direction":"down"},"regions":[{"id":1,"shape":"polygon","points_px":[[536,609],[594,628],[609,701],[563,722],[532,678]],"points_normalized":[[0.34896,0.59473],[0.38672,0.61328],[0.39648,0.68457],[0.36654,0.70508],[0.34635,0.66211]]}],"prompt":"Remove the selected stray lines and refine the edge between the hair and collar."}
Send ↑
AGENT
Editing the selected area…
edited-image.pngLocal edit complete
1 selection
Copy JSON
Area and instructions copied
Before
After
‹ ›
01 / 03 Scroll down to select a detail
Illustrative demo
Skip demo ↓
Open flashmask.net in Chrome or Safari on your computer to start selecting.
How it works
Three moves.
01
1. Drop in your image
Supports PNG, JPEG/JPG and WebP images.
02
2. Circle the spot
Draw an outline, then adjust its position or nodes. Add more regions as needed.
03
3. Copy JSON to your agent
Send the JSON and original image to your agent, or export a black-and-white mask.
On Mac
Native Mac app.
Launch offer $5.99$3.99Buy once · No subscriptionUnlimited tasks · Zero ads
Prices vary by App Store region.
Works offline. Includes all 1.x updates.
Requires macOS 26 or later · Apple Silicon
Private by design
Your images stay local.
Images and editing data stay local, with no uploads or access by advertisers. The Mac app works offline.
Questions?
How the free credits work, what the JSON looks like, which browsers are supported — it’s all in the help center.
New browsers get 3 free tasks, then 1 free task a day, no rollover. If no ad is available, this export is on us.
Rewarded ad · complete
This task is unlocked.
Copy the JSON and export the mask as many times as you like, until you load the next image. Your selections, nodes and prompt are exactly where you left them.
From tomorrow: 1 free task a day. The Mac app is unlimited and ad-free.
Advertisement · rewarded
Ad plays here
Rendered by the ad network in the standard full-screen rewarded format. The ad content itself is not designed by us.
Watch to the end to unlock this task. Your selections, nodes and prompt are kept either way.
All 1.x updates included