How to Draw Points, Lines & Polygons on a Map
What is Capto?
Capto is a free, browser-based tool to graphically create geospatial data, accessible from any desktop or mobile device. Its purpose is to make it easy to draw, describe, and export points, lines, and polygons without installing anything or creating an account.
Key features:
- Draw points, lines, and polygons: Pick a geometry type from the toolbar and draw directly on the map.
- Custom attributes: Attach any number of key/value properties to a feature, in addition to its name.
- Layer management: Organize features into named, color-coded layers. Toggle visibility, labels, color, or delete layers at any time.
- Data persistence: Features, layers, and per-layer label settings are saved in your browser's IndexedDB storage and restored automatically on your next visit.
- Export to GeoJSON or KML: Download your features, with their custom attributes, in the format that suits your workflow — GeoJSON for GIS tools, KML for Google Earth.
- Current location: Place a point at your GPS position with one tap.
- Address search: Look up a place by name and jump straight to it, or add a point there.
How to use the Map Tools?
On the right edge of the screen you'll find a vertical toolbar (left edge, if you switch sides — see below). To keep it short, related tools are collected into groups: a group button shows a small corner arrow, and clicking it opens a panel with the tools inside. These are the buttons always visible on the toolbar:
The Draw tools group draw holds everything that creates or reshapes geometry:
The Modification tools group highlight_alt holds what you can do to the feature you've selected. They all stay greyed out — and so does the group button itself — until you select something on the map:
The Import and export group swap_vert holds getting data in and out:
Choosing a tool closes the group panel. If that tool stays active — the draw tools and all four vertex/move tools do — the group button takes on its icon and turns blue, so you can always see which tool is running without opening the group. Click the group button and pick the tool again to turn it off, or press Esc — for a draw tool that also discards a shape you're halfway through. While the panel is open, pressing Esc or clicking elsewhere only closes the panel, without changing the active tool.
The coordinates readout is separate from the toolbar: it sits at the top center of the screen. At the bottom center you'll find three more buttons — About, Help, and Disclaimer — always available regardless of what else is open.
How to search for an address?
- Click the Search address button search in the toolbar to open the search panel.
- Type a place name or address and press Enter or click the search icon.
- Matching results appear in a list below the search box. Click a result's text to center and zoom the map there — a small round marker previews the location.
- Click the add button next to a result to add a permanent point there. A dialog opens pre-filled with the place name; confirm to save it.
- The round preview marker disappears once you add the permanent point, or when you close the search panel.
- If nothing matches, the panel shows "No results".
Address search uses the free Nominatim geocoding service from OpenStreetMap and requires an internet connection.
How to draw a point, line, or polygon?
- Click the Draw point , Draw line polyline, or Draw polygon button in the Draw tools group draw. It will turn blue to indicate it is active.
- For a point: click or tap once on the map to place it.
- For a line or polygon: click once per vertex, then double-click (or tap the last point again) to finish the shape.
- Put a vertex in the wrong place? While you're still drawing, press Ctrl+Z (or the Undo button undo) to take back the last vertex. Press it again to take back the one before. It only touches the shape you're drawing — nothing you've already saved.
- A dialog will appear. Enter a name, select which layer it should belong to (if you have more than one), and optionally add custom properties (see below).
- Click Add feature to confirm, or Cancel to discard.
- Clicking a different draw button while one is already active switches tools without leaving draw mode.
How to draw a hole in a polygon?
Cut an interior opening out of an existing polygon — a building with a central courtyard, a plaza with a pond — with the Draw hole tool . It doesn't create a new feature; it adds a hole to one that already exists.
- Click the Draw hole button in the Draw tools group draw.
- Click inside the polygon you want to cut a hole into, to place the hole's first vertex.
- Continue clicking to add more vertices, then double-click (or tap the last point again) to finish the hole's shape — same as drawing a regular polygon.
- The hole is added immediately; there's no naming dialog, since it belongs to the polygon you clicked inside, not a new feature.
If the first click isn't inside any polygon, Capto shows an alert and cancels that attempt — the tool stays active so you can just click inside a polygon and try again, no need to reselect it from the toolbar.
A hole's vertices behave exactly like any other vertex afterward: Edit vertices drags them, Add vertex and Delete vertex add and remove them (see "How to move or reshape a feature?" below). A hole ring has the same 3-vertex minimum as the polygon's outer edge. To get rid of a hole entirely, use Remove hole in the Draw tools group rather than deleting its vertices one at a time.
How to snap to existing features while drawing?
While drawing or reshaping any point, line, or polygon, the cursor automatically snaps to vertices and edges of every other feature on a visible layer — no separate tool needed. Get close enough to an existing vertex or edge (a small cursor change is your cue) and click: the new vertex lands exactly on that coordinate instead of a few pixels off. This works for any combination of geometries — two neighboring polygons that share a real, identical boundary instead of a hairline gap; a line that starts exactly where another line ends, so a route stays continuous instead of nearly-touching; a line that starts exactly on a polygon's edge; and so on.
- Snapping works for both drawing (Draw point/line/polygon) and reshaping (Edit vertices) — it considers any feature on any visible layer, including other layers, not just the one you're drawing into.
- Hide a layer (visibility_off in the Layers panel) to stop snapping to its features without deleting them.
- Snapping targets both vertices and the edges between them, so you can also start a new shape exactly on the midpoint of an existing line or polygon side, not only at its corners.
How to add custom properties to a feature?
Any feature — point, line, or polygon — can carry custom key/value attributes in addition to its name, useful for anything a plain name can't capture (elevation, status, a survey date, a note).
- In the Add feature or Edit feature dialog, click + Add property below the Layer selector.
- A row with a Key field and a Value field appears. Fill in both — rows with an empty key are ignored.
- Click + Add property again for as many attributes as you need, or click the close next to a row to remove it.
- Properties are saved with the feature and included in both GeoJSON and KML exports.
If the feature's layer has a property schema defined (see "How to use layers?" below), its fields appear pre-filled automatically — you can still edit, remove, or add more beyond those.
Don't create a property called "name": every feature already has a built-in Name field (the one at the top of the dialog) — it doesn't need to be repeated as a custom property. A property literally named name would just duplicate it.
How to read coordinates on the map?
Click or tap anywhere on the map and its coordinates (latitude, longitude) appear in the readout at the top of the screen, with up to 7 decimal places — no feature needs to be selected.
- Click empty water, land, or any spot on the map to read that location's coordinates.
- Click a point to select it (it turns orange) and read its own exact coordinates.
- Click a line or polygon to select it — the readout shows "Multi-vertex feature selected" instead of a coordinate, since these geometries don't have a single coordinate of their own.
- Click the content_copy icon next to the coordinates to copy them to your clipboard.
How to move or reshape a feature?
Four separate tools, one job each. All of them need a selected feature, and each stays active until you turn it off — click its button again, pick another tool, or press Esc. A second Esc deselects the feature. With Add vertex or Delete vertex, clicking on the map away from the feature also ends the tool and deselects it. Only one runs at a time.
While any of the three vertex tools is running, every vertex of the selected feature is marked with a small orange-ringed dot, so you can see what you're about to drag, click or remove. The dots disappear when you turn the tool off.
Move feature — moves the whole feature without changing its shape: drag it anywhere on the map and every vertex travels together. This is the only one of the four that works on a point — a point has a single vertex, which is the feature, so the other three are greyed out whenever a point is selected.
Edit vertices — reshapes a line or polygon by dragging one vertex at a time. Everything else stays where it is. Snapping applies here too, so a vertex can be dropped exactly onto a vertex or edge of any feature on a visible layer.
Add vertex — click anywhere on a segment of the selected feature and a new vertex appears at that spot, splitting the segment in two. Watch the dots rather than the outline: a vertex added on a straight segment doesn't change the shape at all until you drag it somewhere. The tool stays active, so you can add several in a row. A click on the feature that misses its outline shows a message instead of adding anything; a click away from the feature ends the tool.
Delete vertex — click a vertex of the selected feature to remove it. Also stays active for repeated clicks. Some vertices can't be removed: a line needs at least 2 and a polygon ring at least 3, so at that minimum Capto tells you rather than leaving you with a shape that isn't a valid line or polygon. To get rid of the feature altogether, use Delete feature; to get rid of a hole, use Remove hole.
These four replaced a single "Move feature or edit its vertices" button, which despite its name never moved a line or polygon — it only dragged one vertex at a time. Adding a vertex meant dragging a faint midpoint marker and deleting one meant Alt+click; both were invisible unless you already knew about them, and both are now buttons of their own. Alt+click no longer deletes.
How to look at and edit properties?
Every feature carries a name and, optionally, any number of key/value properties of your own. There are four ways to get at them, for four different moments.
The info panel — select a feature and a small panel appears in the bottom-left corner listing its layer, its geometry and all of its properties, read-only. It follows the selection as you click around, so you can keep working with it open. Close it with close; it comes back the next time you select something. Its Edit… button opens the same editor as the toolbar's Edit feature button.
The Edit feature dialog edit — in the Modification tools group. This is where you add and remove properties on one feature, and where you set its name, its layer and its symbology. See "How to edit a feature?" above.
The attribute table table_rows — every feature of one layer at once, one row each, in a panel docked below the map. Open it from the Layers panel: click a layer's tune button and then Attribute table….
- Columns are the layer's property fields plus any other keys its features happen to carry.
- Every cell is editable. Type and press Enter, or click elsewhere, to save. Esc puts the old value back. This is the quickest way to fill the same field across many features.
- Clearing a cell removes that property from the feature, rather than leaving it there with an empty value. Throughout Capto an empty value means "no value": a property field you leave blank isn't saved onto the feature, and a field that is blank on every feature of a layer isn't shown as a column.
- The my_location button at the start of a row selects that feature on the map; selecting on the map highlights its row.
- Drag the table's top edge to make it taller or shorter — the map shrinks to match, and the size is remembered.
- zoom_out_map in its header frames the whole layer.
Property search search — the same search panel that finds addresses has a second mode, Properties, that searches your own features instead. It matches names, field names and values, so typing a field name like owner lists every feature that has one recorded, whatever the value. Click a result to select that feature and take the map to it. Only visible layers are searched.
How to download features?
Click the Download button download in the Import and export group swap_vert to open the format selector. Choose between GeoJSON and KML.
GeoJSON exports to capto_features.geojson. Compatible with QGIS, ArcGIS, Mapbox, and any GeoJSON-aware tool. Each feature includes its custom properties plus layerName and layerColor.
KML exports to capto_features.kml. Compatible with Google Earth, Google Maps, and GIS tools that support KML. Features are grouped into folders by layer, styled with the layer's color, and custom properties are included as ExtendedData.
When you have more than one layer, the dialog also lets you choose which layer to export. Leave it on All visible layers to get everything, or pick a single layer to export just that one — the file is then named after it. Either way, hidden layers are never included.
How to import features from a file?
Capto reads back the same formats it writes, so you can bring in a GeoJSON or KML file — one you exported earlier, or one produced by QGIS, Google Earth, or any other tool.
- Click the Import button upload in the Import and export group swap_vert and pick a
.geojson,.json, or.kmlfile. - Capto groups the incoming features the way the file organizes them: by the
layerNameproperty in GeoJSON, or by<Folder>in KML. Features with no grouping arrive together as Ungrouped features. - For each group, choose where it lands: Create new layer, or an existing layer of yours. Then confirm with Import.
An import can't be taken back with Undo: what it brings in stays as if it had always been there. Anything you do to those features afterwards — moving, editing, deleting them — can be undone as usual. To get rid of an import that went into a new layer, delete that layer.
Only points, lines, and polygons are imported. Anything else in the file — other geometry types, or a placemark with no geometry — is skipped, and the dialog tells you how many were left out before you confirm.
Custom properties come across as feature properties. A file that Capto itself exported also restores each feature's own color and style overrides, since those travel as reserved properties in GeoJSON and as ExtendedData in KML.
How to delete a feature?
- Click on the feature you want to delete. It will turn orange.
- Click the Delete feature button in the Modification tools group highlight_alt.
- Confirm the deletion in the dialog that appears. The feature will be immediately removed from the map and from storage.
- You can also press the Delete key on your keyboard after selecting a feature.
- Deleted the wrong one? Undo brings it back — see How to undo a mistake?
How to undo a mistake?
Press Ctrl+Z to undo the last thing you did, and Ctrl+Y (or Ctrl+Shift+Z) to redo it. On a Mac, use Cmd instead of Ctrl. The Undo undo and Redo redo buttons near the top of the toolbar do the same; hover over one to see what it would undo or redo — "Undo: Move feature", for instance. A button is greyed out when there is nothing to undo or redo.
Each press takes back one whole action, and you can keep going back — up to the last 100 actions. These can be undone:
- Adding a feature — drawn, at your current location, or from an address search.
- Editing a feature in its dialog: name, layer, properties and symbology, all as one action.
- Editing a cell in the attribute table.
- Deleting a feature.
- Moving a feature, dragging its vertices, adding a vertex or deleting one.
- Drawing a hole in a polygon, or removing one.
- Deleting a layer, which brings back the layer and all its features together.
Some things are not undone: importing a file (see How to import features from a file?), changes to a layer other than deleting it, and anything that only changes what you see — the view, the base map, which layer is active, what is selected.
A few things to know:
- Doing something new after undoing clears the redo list, as in any editor.
- The list lives only while the page is open. Reloading the page or closing it starts a fresh one — your features are still saved, you just can't undo what came before.
- While you're drawing a line or polygon, Ctrl+Z takes back the last vertex of that shape instead (see How to draw a point, line, or polygon?).
- While you're typing in a text field — a name, a table cell, the search box — Ctrl+Z undoes your typing, not the map.
How to move the view around?
The View tools group travel_explore holds three ways of getting the map where you want it. None of them changes your data — they only move the view.
Fit all features — frames every feature on every visible layer at once. Useful after drawing a lot, or when you've wandered off somewhere distant. Features on hidden layers are left out of the calculation.
Fit a layer — asks which layer to frame, then frames just that one. The list shows each layer's colour and how many features it holds; a layer with no features is listed but can't be picked, since there's nothing to frame. A hidden layer can be picked — the list says so, because the map will move to a place where you see nothing until you turn the layer back on. The same thing is available per layer inside the Layers panel, on each row's zoom_out_map button; this one saves opening the panel.
Go to current location near_me — asks your browser where you are and takes the map there, showing the coordinates in the readout at the top. It creates nothing. If you want a feature at your location instead, that's Add point at current location my_location, over in the Draw tools group. Your browser will ask for permission the first time; if you refuse, Capto tells you and the view stays put.
How to edit a feature?
- Click on the feature you want to edit. It will turn orange.
- Click the Edit button edit in the Modification tools group highlight_alt.
- A dialog appears pre-filled with the feature's current name, layer, and properties. You can change any of them — add, edit, or remove property rows the same way as when creating a feature.
- Click Save changes to confirm. If you changed the layer, the feature moves to the new layer instantly.
- If labels are enabled for that layer, the updated name appears on the map immediately.
How to use layers?
Layers let you organize features into named, color-coded groups. The layers panel also controls base map visibility and per-layer label display and appearance.
- Click the Layers button layers in the toolbar to open the layers panel.
- The Base map row at the top controls the background map. Pick a provider from the dropdown — OpenStreetMap (street map), Light (Esri) (a pale base that keeps your own features readable), Topographic (contours and relief) or Satellite (Esri) (aerial imagery) — and your choice is remembered. Click visibility to hide the base map altogether (useful for a clean export or dark background); hiding and choosing are independent.
- The active layer (where new features will be placed) is highlighted in blue. Click any layer row to make it the active layer.
- Use the visibility button to show or hide a layer's features.
- Use the sell button to toggle feature name labels for that layer. The icon turns solid sell when labels are on. This setting is saved per layer.
- A single feature can depart from its layer: click Symbology in the dialog that opens when you add or edit it. The same three groups appear, each behind a Custom … tick box — colour and fill, label style, and line (the fill and the separate outline colour only for polygons, the line section only for lines and polygons). While a box is unticked its controls are greyed out and show what that feature inherits from its layer, so any later change to the layer follows through; ticking it pins those values to that one feature. The button itself reports the state, so you can tell at a glance whether a feature is inheriting or overriding without opening the dialog.
- Use the zoom_out_map button to zoom the map to fit all features in that layer.
- Click the color circle to change a layer's color. All its features — points, lines, and polygons alike — update instantly.
- Use the tune button to open that layer's settings, which has two sections. Symbology… opens a dialog with everything that controls how the layer looks: its colour and fill, where the fill percentage is the opacity of that colour inside polygons; the label colour, size and halo — the halo is a white outline that keeps text readable over a busy map, and it's on by default; and the line, meaning stroke width, pattern (solid, dashed, dotted, or dash-dot) and — for polygons — its own colour, so an outline can differ from the fill it surrounds. Leave that colour alone and the outline simply follows the main colour. Points are drawn from an icon, so neither line nor fill affects them. Note that KML has no way to describe a dash pattern, so a dashed line exported to KML opens as a solid line in Google Earth; re-importing that file back into Capto restores it. Below it, Property fields… opens a second dialog for that layer's property schema — a list of field names (e.g. "species", "height") that come pre-filled whenever you add a feature to this layer. Click add to add a field, close to remove one, and Save when you're done; pressing Enter in a field name starts the next one. The button itself tells you how many fields the layer has. This is just a starting point — features can still have extra fields beyond the schema. Don't add a field called "name" — every feature already has one built in (see "How to add custom properties to a feature?" above).
- Use the edit button to rename a layer inline.
- Use the delete button to delete a layer and all its features. Undo brings the layer back with every feature it held, in its place among the others. Other changes to a layer — its name, colour, symbology, fields, order or visibility — are not undone; change them back the same way you changed them.
- Click + Add layer at the bottom to create a new layer with a custom name and color.
How to add a point at my current location?
- Click the Add point at current location button my_location in the Draw tools group draw.
- If prompted, allow the browser to access your location.
- The map centers on your estimated location and shows a small round marker there, along with a dialog asking for a name, layer, and optional properties.
- Fill in the dialog and click Add feature to accept the location, or Cancel to discard it — either way, the round preview marker disappears once you decide.
If geolocation is denied or unavailable, the app will notify you with an error message. This tool always creates a point — for lines and polygons, use the draw tools above.