How to Use Astroseek Birth Chart URL Parameters
I spend most of my time dealing with astrology software APIs and chart-generation endpoints. Astroseek is one of the few platforms that actually exposes its URL parameters openly, which makes it useful if you ever need to programmatically generate charts or share exact configurations with other people. The system works by appending query parameters to the base chart URL. When you fill out the form on the site, Astroseek quietly builds those parameters into the address bar. Most people never notice this, but once you start looking, it opens up a lot of practical options.
The Power Of Astroseek Birth Chart URL Parameters Unlocking The Secrets Of Your Birth Chart
Here is how the main parameters break down in practice: dat — Date of birth in YYYY-MM-DD format. For example, 1990-06-15. tim — Time of birth in HH:MM format. You use 24-hour clock time here, so 14:30 for 2:30 PM.
lat and lon — Geographic coordinates of the birth location. These are decimal degrees. New York would be roughly 40.7128 for latitude and -74.006 for longitude. city — The city name, usually in English. This is mostly cosmetic since the lat/lon pair actually determines everything, but Astroseek uses it for display purposes. system — The ephemeris system. Default is "default" (Placidus houses with standard planetary positions). You can also set it to "astraea" or "swiss" depending on what backend you want. The Placidus system is the default for most Western astrologers.
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house — House system override. If you need whole sign houses, "whole_sign" instead of the default. Other options include "krishna_murti" and "equal." aspect — Whether to display aspects. Set to "yes" or "no." If you are building lightweight chart images or automated scripts, you can turn aspects off to reduce processing. When I first started using these parameters, I was generating charts for a client who had been born in a timezone that changed during their lifetime. They were born in 1947 in what is now Bangladesh, which was East Pakistan at the time, and the timezone offset was different. Astroseek's default handling of historical timezone data is not perfect. I found that manually calculating and entering the UTC offset using the lat/lon combination, then adjusting the time back by the historical offset, gave me the accurate result. The workaround was to use an online historical timezone database, determine the correct GMT offset for that date and location, and then adjust the time parameter manually before feeding it into the URL.
This is a fairly common edge case if you are working with anyone born before the 1970s in South Asia, parts of Africa, or places that had DST changes that were not consistently recorded. Astroseek does not query a historical timezone database the way more professional software like Solar Fire or Astro.com does. For casual chart generation this is fine. For serious client work, you need to handle this yourself before constructing the URL. Another thing that catches people off guard is how Astroseek handles seconds in the time parameter. The tim parameter accepts HH:MM, and any seconds get silently dropped. If your client gives you a birth time like 08:47:23, you should round it to 08:47 before putting it in the URL. The difference will not show up on the chart unless you are working with very tight orb calculations where a 23-second difference could shift a planet from one degree to another. That rarely matters in practice, but it matters if you are doing precision work. You can also combine these parameters with chart type parameters. Adding charttype=basic gives you a standard natal chart view. If you want a transit chart, you add the transit date parameters like t_date, t_time, and t_lat/t_lon. This is useful if you are building a page that shows current transits over a natal chart without manual entry.
The main limitation here is that Astroseek does not expose every possible parameter publicly in any kind of clean documentation. You figure out the parameter names by looking at the URL after you generate a chart on the site. This reverse-engineering approach works well enough, but it means if Astroseek changes their parameter names in an update, your existing URLs break. I have seen this happen. The site updated their system once and the system parameter stopped working the same way for a few weeks while they adjusted their backend. Always test your generated URLs after any major site update. Another practical issue is that Astroseek URLs can get long very quickly. A full natal chart URL with all parameters is usually around 300 to 500 characters. If you are sharing these in emails or on social media, they look messy. There is no URL shortener built into the platform. I just use a standard service like Bitly for this. Nothing fancy. If you need something more robust than Astroseek for programmatic chart generation, the Swiss Ephemeris API through Astro.com is the better long-term solution. It has proper timezone handling, historical accuracy, and a documented API. But it costs money and requires registration. Astroseek is free, which is why it remains useful for quick chart generation even with its limitations.
The biggest takeaway is that you should always verify the chart that gets generated matches what you expect. Generate the URL, open it in a new tab, and check the birth data displayed on the chart page. It takes about ten seconds and saves you from sending incorrect charts to people. I learned this the hard way after accidentally swapping the latitude and longitude values for a client born in Sydney and nearly sending them a chart for a location in the South Atlantic Ocean. The parameters accepted the invalid coordinates without any error message, which is another thing you need to watch out for.
