Stand on the spot you want to remember and tap Mark Here.
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Do something
Your kit
Your sites
Latest marks newest first
Recent Activity
Last marked
No marks yet.
Nearest to you
Mark something to see distance.
Field tip of the day
Open the Field Reference for GPS know-how.
Backup & Data
Back up all your data or restore from a previous backup. Stored entirely in this browser — clearing browser data will erase it.
All marks
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⬆️ Bring your marks — GPX · KML · GeoJSON
Import waypoints and boundaries from Garmin, onX, Gaia, Google Earth, or another Mark Once install. You see a preview first — nothing is saved until you confirm.
Type library
The mark types this tool knows — each with an icon, a color, and a field tip. Add your own.
Mark types
0 mark types — add your own
Keep the app open — a locked phone in a pocket can't hear GPS; if it happens anyway, the trail marks the gap honestly.
Recorded paths (0)
Saved zones
0 zones
Mark a corner only
Saved as a mark — findable, and offered in the mark picker. No zone.
Know before you dig
Field reference
Real field-GPS know-how — accuracy, declination, re-averaging, and the 811 call-before-you-dig rule.
Before you head out
Field kit
What to bring before a marking session — including the before-you-dig steps.
Yours to tune
Settings
Configure your tool and manage your license.
🏷️ Report branding CREW
Put your outfit's logo and business line on every printed site report — the page a customer keeps wears your name, not ours. Included with the Crew license.
🔒 Crew feature · about licenses →
Both print on the head of every site report. Leave either empty to skip it.
🌗 Display
Night vision red-shifts the whole screen so your eyes keep their dark adaptation — it is also a slot on the field bar's second page, one tap, without looking.
⚖️ Terms & legal
Mark Once is published by AMZE LLC (contempl8.studio). Licensed for single-user personal use; the app, its code and its data stay on your device.
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⚠️ Safety. This tool records where you put something and walks you back to it. It is not a utility locate and does not detect anything underground. Call 811 (or your national equivalent) before any digging, and treat every mark as a reminder, not a guarantee.
📍 Location & GPS
Marking and the compass need your device's location. Connect it once below — GPS works fully offline and in airplane mode, and your marks are never sent anywhere. (The 🛰️ Satellite map is the one exception: it streams USGS imagery for the area you're viewing. Switch it off on the Map and the app touches nothing.)
On a phone or tablet, tap Allow when prompted. If you blocked it before, tap the 🔒 / ⓘ in the address bar → Location → Allow, then press Enable again. Most common issue: the browser only prompts for location on a secure page — https://, localhost, or the downloaded file. Over plain http on a phone (a LAN address) it stays silent. The live site and your downloaded copy are both fine. A desktop without GPS hardware will show low accuracy.
🎯 Marking defaults
Pre-fill these every time you tap Mark Here — set them once and map a whole site fast.
typical range $150–$400
🗂️ Your data
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Everything is stored only in this browser — clearing browser data erases it. Back up regularly, and export to your map app for the field.