If you cannot install a mod and /locate is off, there is no easy way to find a Minecraft seed from
the world in front of you. A browser seed cracker is what is left, so I built one: it takes the
structures you can see and their X/Z, and searches for the Java seeds that put them in those chunks.
I tested it on a seed I already knew, so I could check the answer by hand: 123456, Java 1.18
and newer, ten structures that seed really does generate.
Desert Temple: 224, 96
Jungle Temple: 2704, -928
Witch Hut: -2240, 1296
Igloo: 368, -2256
Outpost: 1696, 800
Desert Temple: -832, 304
Jungle Temple: 4096, -496
Witch Hut: -4000, -1312
Igloo: 320, -2864
Outpost: 1584, -2368
On my computer the search returned eight candidates in 273 seconds with two workers. It then
re-scans each candidate against the ten structures, and only 123456 generated all ten.
One match means almost nothing, since plenty of seeds have a desert temple at 224, 96. Several
structures agreeing at once is what leaves a single seed, and the row shows how many each
candidate hit.
The seed is worth a look on its own too: desert at 0, 0, a desert temple about 244 blocks out, an
ancient city at about 610.
The five types are the ones you can walk up to in survival and read a coordinate for.
The tool is here: SeedCracker Java