Most common leak point on the Rangers is the 3rd Brake light on the back of the cab
And yes it shows up in the front on both sides

Lots of videos and how-tos on checking and then fixing this issue

Google: 2001 ford ranger 3rd brake light leak repair

 

Same problem with a 2000, The thing that helped me the most was running silicone all around my outer door seals and the windshield and rear window seals. Seems the door seals were coming loose and the gasket around my old windows was leaking like crazy. Until I can have the glass pulled and new seals put in, it's stopped the water. I also ran it around the 3rd brake light for good measure after i replaced the seal there. Oh and there's a little felt pad that blocks the drain holes in the front fenders for the water that accumulates under the wipers

 

thank you but i know for fact it's not the third light causing this issue. Back in 2014 I removed all hardware and sealed it tight cause I thought other water leak issue was coming from that. Turned out it wasn't the third light then it was the back sliding window weather strip was cracked. Thank you again.

 

As I just replied to another about the third brake light that's not the culprit with this issue. I also know for a fact that the windshield and rear window aren't the culprit either. It could be the small windows of the suicide doors (?). However I did go back out to the truck this evening after I vacuumed all the water out earlier this afternoon, it had rained just minutes before I went out and yet again the floorboard was in a nicely filled puddle of water. I began looking at the body seals around the door, it is nasty looking so that maybe the culprit. Anyway I'm gonna try that first. I was just gonna replace all seals but after seeing what they cost are they freakin crazy it's rubber for pete-sakes. I'm hoping I can remove the old seals without killing them, cleaning up the area, placing a nice thick bead of silicone around the area and putting the old seal back inplace. What do you think? As for the "little felt pad that blocks the drain holes in the front fenders for the water that accumulates under the wipers" can ya post a pic of this? I'm gonna start on the body seals around the doors Thursday and trust me when I say about 12 hrs afterwards I'll take and run water over it for half hour or more. If I don't get water then problem solved and I'll get back to ya letting ya know how it went either way. Thanks in advance for all the help

 

fender drain hole
he calls it plastic it was more felt like. It keeps the water under the wipers from flowing out the fenders freely. and you can accumulate leaves and stuff as this guys video shows.
This pools up behind the dash and can run in from the heater vents or through wiring holes