Regex to Match Latitude and Longitude

This regex validates geographic coordinate pairs in the format latitude,longitude. Here is the token-by-token breakdown:

^ — Anchors the match at the start.

-? — Optional minus sign for negative latitudes (southern hemisphere).

(?:90(?:.0+)?|[0-8]?\d(?:.\d+)?) — Matches valid latitude values (-90 to 90):

• 90(?:.0+)? matches exactly 90, optionally with decimal zeros (90.0, 90.00)
• [0-8]?\d matches integers 0-89 (the optional [0-8] handles tens digit)
• (?:.\d+)? adds optional decimal places

,\s* — Matches a comma followed by optional whitespace, separating latitude from longitude.

-? — Optional minus sign for negative longitudes (western hemisphere).

(?:180(?:.0+)?|(?:1[0-7]\d|\d{1,2})(?:.\d+)?) — Matches valid longitude values (-180 to 180):

• 180(?:.0+)? matches exactly 180 with optional decimal zeros
• 1[0-7]\d matches 100-179
• \d{1,2} matches 0-99
• (?:.\d+)? adds optional decimal places

$ — Anchors the match at the end.

This pattern validates coordinates like 40.7128,-74.0060 (New York), -33.8688,151.2093 (Sydney), and 0,0 (Gulf of Guinea). It ensures latitude stays within -90 to 90 and longitude within -180 to 180.