"It was working fine until yesterday." - Something anyone who has operated a crawler has said at least once
Reading Time: 7 minutes | Last Updated: January 2026
The lifespan of a crawler is shorter than you think
When you first create a crawler, everything runs perfectly. Data comes in cleanly, and the scheduler works well.
But as time goes on, the following happens:
- 1 week: No issues. "I did a great job after all."
- 1 month: Empty data starts coming in from certain pages.
- 3 months: No errors, but the collected data is strange. IP gets blocked.
- 6 months: Site redesign causes half of the crawler to stop working.
It's not that the crawler is breaking. The website keeps changing.
This article explains why websites constantly change and why crawler maintenance becomes an endless battle technically.
Real Case: E-commerce Price Monitoring Crawler
A company developed a crawler to monitor competitor prices on 3 open markets (Coupang, 11th Street, Gmarket).
First 3 months: Works perfectly. An Excel report is automatically generated every morning.
Month 4: Coupang redesigns its frontend. The crawler starts returning empty data, but it takes a week for the responsible person to notice. It takes 3 days to fix.
Month 6: 11th Street strengthens bot detection. IP blocking begins. Proxy service is introduced, but incurs an additional cost of 300,000 KRW per month.
Month 9: Gmarket changes API response structure. JSON parsing breaks. Outsourced developers are asked for fixes, taking 2 days to understand the code and 3 days to fix. Cost: 1.2 million KRW.
Total cost after 1 year: Initial development 3 million KRW + maintenance (4 fixes) 4.8 million KRW + proxy 1.8 million KRW = 9.6 million KRW. Three times the initial estimate.
The company eventually switched to a subscription-based crawling service. The reason is simple: A predictable monthly fee is better for business than unpredictable maintenance costs.
7 reasons why websites change
1. Frontend Redesign
The most common cause. Companies regularly change the frontend for UX improvement, branding, and performance optimization.
- Frequency: Large sites redesign 1-2 times per quarter
- Impact: HTML structure, CSS class names, entire DOM tree change
- Impact on crawlers: Selector-based parsing breaks entirely
Large sites like Naver, Coupang, and 11th Street change their frontends frequently. After the introduction of SPA frameworks like React and Vue.js, crawling difficulty has significantly increased due to the mix of SSR and CSR.
2. A/B Testing
Large sites always run A/B tests. Even with the same URL, different HTML is served to each user.
- Frequency: Ongoing (dozens of tests simultaneously)
- Impact: Structure changes every time you access the page
- Impact on crawlers: Results vary each time you collect data, making debugging difficult
A significant portion of the "worked fine yesterday, not today" phenomenon is due to A/B testing. The DOM structure can vary significantly depending on the test group.
3. Bot Detection/Block Enhancement
Websites continuously upgrade their bot detection systems.
- Technologies: Cloudflare, Akamai Bot Manager, PerimeterX, DataDome
- Detection methods: IP patterns, browser fingerprinting, behavior analysis, JavaScript challenges
- Update frequency: Rule changes 1-2 times per month
In particular, Korean sites like Naver and Coupang operate their own bot detection systems, continuously strengthening block rules. User-Agent and header combinations that passed yesterday may be blocked today.
4. API Endpoint Changes
Even if the frontend remains the same, if the internal API changes, the crawler breaks.
- Types: API version updates, parameter changes, response structure changes
- Frequency: With each backend deployment (1-2 times per week)
- Impact on crawlers: JSON parsing failures, authentication method changes
Crawlers that directly call REST APIs are particularly vulnerable. Companies do not expose internal APIs, so you cannot know about changes in advance.
5. Authentication/Security Policy Changes
Sites requiring login periodically change authentication methods.
- Types: Adding 2FA, shortening session expiration times, adding CAPTCHA, changing token methods
- Frequency: 1-2 times per quarter
- Impact on crawlers: Automated logins break
Financial and public institution sites have short security reinforcement cycles and often apply changes without prior notice.
6. Changes in Dynamic Content Loading Methods
Loading content with JavaScript is becoming increasingly complex.
- Types: Lazy Loading, Infinite Scroll, Real-time updates based on WebSocket
- Trends: Static HTML → AJAX → SPA → SSR/ISR Hybrid
- Impact on crawlers: Unable to fetch data with simple HTTP requests
The number of sites requiring the use of Headless browsers (Puppeteer, Playwright) is increasing every year, raising the cost and complexity of crawling.
7. Legal/Policy Changes
Changes in robots.txt, updates to terms of service, and enhanced access restrictions also affect crawlers.
- Types: Adding crawling restrictions to robots.txt, strengthening rate limits, region-based access restrictions
- Frequency: 1-2 times per half year
- Impact on crawlers: Narrowing the legal data collection scope
Site Change Frequency by Type - Observations over 7 years
Hashscraper has crawled over 5,000 sites in 7 years. Here are the observed change frequencies by site type:
| Site Type | Frontend Change Frequency | Crawler Modification Frequency |
|---|---|---|
| Large E-commerce (Coupang, 11th Street) | Weekly to Biweekly | 2-4 times per month |
| Portals (Naver, Daum) | Biweekly to Monthly | 1-2 times per month |
| Social Media (Instagram, X) | Monthly to Bi-monthly | 1-2 times per month |
| Public Institutions/Financial | Quarterly to Bi-annually | Quarterly to Bi-annually |
| Small Shopping Malls | Bi-annually to Annually | Bi-annually to 1-2 times per year |
Key: The larger the site, the more frequent the changes. If you operate 10 crawlers, you need to make adjustments to at least 1-2 of them every week.
Is our company's crawler okay? - Self-diagnosis
If three or more of the following apply, it's time to reassess your crawler maintenance strategy:
- [ ] The crawler suddenly stopped working within the last 3 months.
- [ ] Developers manually edit the code with each site change.
- [ ] It took over 24 hours to notice a crawler failure.
- [ ] Proxy costs are increasing.
- [ ] Using a separate service due to CAPTCHA bypass.
- [ ] Only one person understands the crawler code.
- [ ] Spending over 4 hours per day on crawler maintenance.
5 or more apply? There's a high chance that your current costs are higher than a professional service.
Hidden Costs of Crawler Maintenance
Actual costs incurred when operating a crawler directly.
Initial Development Cost
| Item | Cost |
|---|---|
| Crawler Development (Simple Site) | 500,000-1,000,000 KRW |
| Crawler Development (Complex Site) | 2,000,000-5,000,000 KRW |
| Headless Browser Setup | +500,000-1,000,000 KRW |
| Proxy/Bypass Construction | +500,000-2,000,000 KRW |
Annual Maintenance Cost (per crawler)
| Item | Monthly Cost | Annual Cost |
|---|---|---|
| Site Change Response (1-2 times per month) | 500,000-1,000,000 KRW | 6,000,000-12,000,000 KRW |
| Server/Infrastructure | 100,000-300,000 KRW | 1,200,000-3,600,000 KRW |
| Proxy Cost | 100,000-500,000 KRW | 1,200,000-6,000,000 KRW |
| Monitoring/Failure Response | 200,000-500,000 KRW | 2,400,000-6,000,000 KRW |
| Total | 900,000-2,300,000 KRW | 10,800,000-27,600,000 KRW |
If you operate 10 crawlers, the annual cost is 10 million to 28 million KRW. Adding developer salaries (60-120 million KRW per year), the actual cost of direct operation becomes apparent.
Comparison of Solutions
| Method | Cost | Response Speed | Pros | Cons |
|---|---|---|---|---|
| Hiring Dedicated Staff | 60 million-120 million KRW per year | Immediate | Full control | Difficult to hire, limited by one person |
| Outsourcing for Issues | 50,000-150,000 KRW per case | 3-7 days | Cost only when needed | Slow, quality variance |
| Subscription Service | 300,000 KRW per month and up | Within 24 hours | Predictable, access to experts | No ownership of code |
| Credit-based Self-serve | 30,000 KRW per month and up | Immediate (pre-built) | Inexpensive, immediate start | Limited to specific sites |
1-2 crawlers: Outsourcing or credit-based options are sufficient.
3 crawlers or more: Dedicated staff or subscription services are cost-effective.
Getting started: Credit-based services start at 30,000 KRW per month, making it easy to test without a heavy initial investment.
Conclusion
Creating a crawler is not a one-time task. The web is a living ecosystem, and sites change weekly.
The key question is not "how to eliminate maintenance costs" but "who will handle maintenance, in what structure, and at what cost."
When you honestly calculate the hidden costs of direct operation, the answer is surprisingly clear.
Next Steps
- Test with Credits - Start from 30,000 KRW/month, use pre-built bots
- Free Consultation for Subscription - If you need custom crawling
If you want to focus on data without worrying about maintenance, Hashscraper is here to help.
Hashscraper - Expert team that has crawled over 5,000 sites in 7 years
