You're past your data cap. Your ISP is throttling you.
Many cable and satellite providers cap your monthly data — usually 1.2 TB on cable, much less on satellite — and silently throttle you once you cross it. Speeds can drop from full plan to 1–3 Mbps. This is by far the most under-diagnosed cause of 'it gets slow toward the end of the month.'
Log in, look for current-cycle data usage. If you're over the cap, that's your answer.
Unlimited add-ons typically cost $30/mo more on cable. If you're consistently over the cap, switching to an uncapped ISP (most fiber providers) is often cheaper long-term.
AT&T Fiber, Verizon Fios, Frontier Fiber, Google Fiber, and most other fiber ISPs don't impose data caps. If you've outgrown a capped plan, that's a clean reason to switch.
ZIP for quick check, or full address for census-block precision.
Try any US ZIP — we query the live FCC dataset. Example: 29680, 78704, or 94110.