See how cities really compare, on one map at true scale
Put two cities on the same map, drag one over the other, and see the difference at once. Comparison pages add population and density; a link reopens the same cities for anyone you send it to. Free, in the browser — up to ten cities with an account.
The challenge
City statistics are easy to find but hard to feel. A population number or square-kilometer figure does not tell you how large a place feels relative to another, especially across countries and continents.
The approach
CompareCitySizes renders cities as true-scale overlays on one map. You pick two, drag one over the other, and see the difference at once; the comparison pages add population and density beside the area. A link reopens the same cities for anyone you send it to.
Type a name, pick the right place from the suggestions. The map centres on it.
The next city lands on the first, at the same scale. Drag either one to line them up.
Each city’s area sits in the sidebar; the overlap tells the rest. Rotate a shape if it helps.
Copy the link into an article, a lesson or a chat. Whoever opens it gets the same cities.
Cities render at geographic scale on the same basemap, so “bigger on screen” means bigger in reality, not a cropped screenshot at different zoom levels.
Turn a shape in 15° steps or with a slider so it sits along a coastline or a river the way the city you are comparing it with does — a fairer read of the overlap.
Two without an account, ten with one — capitals, metro regions or peer cities on a single canvas.
Share copies a link that reopens the same cities for whoever follows it — in an article, a lesson or a group chat.
Every pairing has its own page with area, population and density side by side — the table for when the shape is not enough.
Runs in any browser, phone included. No GIS licence, no download, no sign-up to start.
Curious people, mid-argument
Most visitors arrive from a search for exactly this — “city size comparison” — put New York, Tokyo or London on the map and start dragging. Dragging is the product: 260,000 drags by 13,000 people in one summer, about twenty each.
Teachers and students
Educators find it on their own: a public education portal sent a class-sized burst of visits over three days, and lesson platforms and Teams links keep showing up in the referrers. Two cities, one map, no account — it works on the projector and on the students’ phones.
Anyone who wants the number
The GDP, population, density and largest-cities pages answer the question on the page — over a thousand visits a month come for the table, not the map. A quarter of the largest-cities readers go on to the map.
Journalists and explainer writers
Not yet where most visitors come from, but what the tool was built for: a true-scale overlay makes a point a table cannot, and a shared link reopens the same cities inside the story.
People search for exactly what the site is: “city size comparison” is the top query, and the map ranks in the top three for it. The ranking pages for GDP, population and largest cities bring their own search traffic. Search clicks grew five-fold in a year, from about 2,200 a month to 11,000.
Underneath, every city pairing has its own page — title, description, canonical URL, structured data — 373 of them. They already rank in positions three to six; pair-by-pair demand is still small, so they are an investment ahead of the query.
Running a product is most of the work of having one. So alongside the map we built the panel it needs: a support inbox that grew into a mail client, an editor for the city shapes, and the cache that keeps lookups fast.
Feedback & support
Bug reports find what tests miss; feature requests say what to build next. Rather than bolt on a helpdesk, support lives in the product’s own admin panel.
Fills in the contact form (General Feedback · Bug Report · Feature Request) — or simply emails support@comparecitysizes.com.
Every message becomes a ticket, categorized and stored with its full email history. Direct emails are received by AWS and threaded automatically, even when the user replies from their phone.
Opens the admin Feedback tab, filters by open / bug / feature, reads the whole conversation, and replies from the panel. The reply goes out from support@ and stays on the ticket.
No shared Gmail password, no Zendesk seat, no messages lost in a personal inbox. One source of truth, run from a browser.
Typed feedback, not a free-text blob
Bug, feature and feedback categories each ask the user for the right details up front — reproduction steps for bugs, the ‘why’ for feature requests.
Real email threading
Standard Message-ID / In-Reply-To headers plus a plus-address fallback (support+ticket@) keep replies attached to the right ticket regardless of the user’s mail client.
Grew into a full mail client
The same pipeline now handles every @comparecitysizes.com address in a Gmail-style Email tab: auto-detected mailboxes, threaded reading pane, compose from any domain address, templates, and sending to registered users.
Shape editor
Every comparison rests on the outline the map draws, and the outlines come from OpenStreetMap — which sometimes hands back a region for a town, or an airport for a city.
So any boundary can be opened in an editor on the map: draw a polygon point by point or freehand, drag its vertices, combine several into one shape, undo and redo, or paste GeoJSON. Save, and the corrected outline is what every visitor sees from then on.
Draw or trace
Point-by-point polygons for precision, freehand for speed; several polygons combine into a MultiPolygon for cities with islands or exclaves.
Overrides beat the source
An edited boundary is stored as an override, so a later refresh from OpenStreetMap never quietly puts the wrong shape back.
Closes the loop with support
A “wrong outline” bug report is fixed in the same panel it arrived in — open the ticket, open the city, redraw, reply.
Metadata alongside
Area, population, coordinates and a note travel with the shape, so the comparison page updates with it.
Caching
City outlines come from Nominatim, OpenStreetMap’s geocoder — slow, rate-limited, and not something to call every time someone types “Tokyo”. So every boundary is stored in the site’s own database on first use and served from there afterwards; repeat lookups never leave the server.
Today that cache holds 20,948 city boundaries, each with its source recorded. It is the same table the shape editor edits: an override is simply a cache entry a human has corrected.
What we did
Outlines are administrative boundaries as mapped in OpenStreetMap, and a few are flagged approximate in the app. They are right for comparison and teaching, not for legal, survey, planning or statistical use.
Yes — up to ten on one map once you sign in with Google, Facebook or email. The shared link reopens the whole set.
No. Comparing two cities and sharing the link works without one; an account lifts the limit to ten.
Open the product, or talk to us about building something similar for your team.