Scraping carries one constant risk: getting blocked. Sites run defences to stop mass extraction, and tripping them can cost you an IP, an account, or access to a whole domain. The good news is that bans aren't mysterious — they're triggered by recognisable patterns. Understand the triggers and the prevention is mostly common sense.
Why bans happen
Sites watch for behaviour that doesn't look human:
- Too many requests from one IP — a flood from a single address reads as a DDoS-style attack and gets cut off.
- Missing or suspicious headers — especially the User-Agent. Absent or odd headers signal a bot.
- Perfectly even timing — identical gaps between requests are a dead giveaway of automation; humans are irregular.
- Ignoring
robots.txt— hitting pages the site marked off-limits gets you blacklisted. - Reusing one address — modern sites track per-IP activity and act when it looks abnormal.
- Skipping an available API — pulling from pages when an official API exists invites sanctions.
- Other bot tells — navigating too fast, repeated failed captchas, and similar unnatural patterns.
How to tell you've been blocked
The signs are usually clear:
- 403 Forbidden — the request was rejected, often for bad headers or forbidden pages.
- 429 Too Many Requests — you've exceeded the rate limit.
- Sudden slow responses — soft throttling before an outright block.
- Captcha or a login redirect — an anti-bot system kicked in.
- Empty or stub responses — the site may be feeding bots fake or blank data, or it changed structure.
- Your IP appears on a blacklist — once flagged, the address may be restricted across a whole network, not just one site.
How to prevent it
The countermeasures map directly onto the triggers.
Use clean proxies. Routing through different IPs masks the source and spreads load so no single address hits a limit. A clean, dedicated address that isn't already burned by someone else is the foundation — public and free proxies are usually flagged before you start.
Control your request rate. Add pauses, and crucially, vary them — irregular gaps look human, fixed intervals look automated. Don't hammer the server.
Behave like a person. Random delays, moving around the site, following links, occasional scrolling — unpredictable actions read as natural where rigid patterns don't.
Rotate User-Agents. Varying headers makes requests look like they come from different browsers and devices instead of one tireless bot. Keep them realistic and diverse.
Handle captchas sensibly. Anti-captcha services can clear challenges automatically when you hit sites that gate on them, keeping the run from stalling.
Optimising the whole process
A few habits make scraping both safer and lighter on the target:
- Use several IPs so activity isn't concentrated on one address.
- Rotate headers so requests appear to come from many users.
- Respect
robots.txt— reading the rules avoids needless risk. - Store data locally and cache so you don't re-request what you already have, cutting load and exposure.
The bottom line
Sites ban scrapers to protect their resources, and the way to stay unblocked is to not look like a threat: clean IPs, reasonable and irregular request rates, realistic headers, and human-like behaviour. Do that and you collect data reliably while staying within the rules. The proxy layer is the part that quietly carries the most weight — a stable, clean, dedicated address gives you a predictable foundation that shared, already-flagged pools can't.