Seat Ibiza Brake Fluid Loss and Spongy Pedal

Low brake fluid and spongy pedal usually means worn brakes. Have you checked the pad and disc thickness? Any visible leaks in the lines or around the master cylinder? Does the brake system light come on?

The warning light coming on during hard braking pretty much confirms low fluid from increased volume in the calipers as the pads wear. While other issues are possible, worn brakes are most likely. I'd suggest a workshop inspection and replacement if needed.

Thanks! I haven't checked the brakes myself. I don't see any leaks, and the lines look okay. But the brake system light does come on sometimes, especially when braking hard. Could it be something else, or does it still sound like the brakes?

Just letting you know, you were right. The garage confirmed worn brakes. Replaced them and the brake fluid, and the pedal feels normal. Cost 480€, but it's fixed. Thanks for the help.