MJ12bot: Majestic Backlink Crawler

What is MJ12bot?

MJ12bot is the web crawler operated by Majestic, a specialized SEO company focused on backlink analysis and link intelligence. It’s one of the largest and most active crawlers on the web, continuously mapping the internet’s link structure to build Majestic’s comprehensive backlink index.

Purpose of MJ12bot

MJ12bot crawls the web to power Majestic’s link intelligence tools:

• Backlink discovery: Map and index billions of backlinks
• Link graph analysis: Understand link relationships and authority flow
• Trust Flow & Citation Flow: Calculate Majestic’s proprietary metrics
• Historical data: Track link changes over time
• Competitive analysis: Provide link profile comparisons
• Topical Trust Flow: Categorize sites by topic relevance

How MJ12bot Works

MJ12bot operates as one of the most comprehensive web crawlers:

1. Discovers URLs through links, submissions, and web exploration
2. Crawls pages to extract links and content
3. Analyzes link structure to build the link graph
4. Calculates metrics like Trust Flow and Citation Flow
5. Updates index continuously with fresh data
6. Tracks changes to monitor link profile evolution

The crawler is known for its:

• High crawl volume (one of the most active crawlers)
• Deep crawling capabilities
• Historical data preservation
• Focus on link relationships rather than content

User Agent

MJ12bot identifies itself as:

Mozilla/5.0 (compatible; MJ12bot/v1.4.8; http://mj12bot.com/)

The version number may vary as the bot is regularly updated.

Is MJ12bot Good or Bad?

Pros:

• Specialized expertise: Best-in-class backlink analysis
• Respects robots.txt: Follows webmaster guidelines
• Well-documented: Clear information and support
• Legitimate service: Powers professional SEO tools
• Historical data: Valuable for tracking link changes over time
• Widely used: Trusted by SEO professionals globally

Cons:

• Very aggressive crawling: One of the most active crawlers
• High bandwidth usage: Can consume significant resources
• Frequent visits: May crawl multiple times per day
• Competitor intelligence: Exposes your backlink strategy
• Not a search engine: Won’t improve search rankings
• Resource intensive: Can impact server performance

Should You Allow MJ12bot?

This depends on your priorities and resources:

Allow MJ12bot if:

• You use Majestic for your own SEO research
• You want comprehensive backlink data
• You have sufficient server capacity
• You value visibility in link analysis tools
• You want to track your historical link profile
• You’re building links and want them indexed

Block MJ12bot if:

• You have limited bandwidth or server resources
• You’re experiencing server performance issues
• You want to hide your link strategy from competitors
• You prefer to keep your backlink profile private
• You don’t use Majestic tools
• You’re in a highly competitive niche

How to Block MJ12bot

Using robots.txt

Block completely:

User-agent: MJ12bot
Disallow: /

Block specific sections:

User-agent: MJ12bot
Disallow: /admin/
Disallow: /private/
Disallow: /api/
Allow: /

Server-Level Blocking

Nginx configuration:

# Block MJ12bot
if ($http_user_agent ~* (MJ12bot)) {
    return 403;
}

Apache .htaccess:

# Block MJ12bot
RewriteEngine On
RewriteCond %{HTTP_USER_AGENT} MJ12bot [NC]
RewriteRule .* - [F,L]

Crawl Rate and Impact

Typical Activity:

MJ12bot is known for being one of the most aggressive crawlers:

• 2000-10,000+ requests per day (varies significantly by site)
• 200MB-1GB+ daily bandwidth consumption
• Multiple visits per day to active sites
• Deep crawling of internal link structure
• Follows most links regardless of importance

Resource Impact:

MJ12bot typically has the highest impact among SEO crawlers:

• More aggressive than AhrefsBot
• Much more active than SemrushBot
• Significantly higher volume than Moz DotBot
• Can cause noticeable server load on smaller sites

Controlling Crawl Rate

1. Robots.txt Crawl-Delay

User-agent: MJ12bot
Crawl-delay: 30

MJ12bot respects crawl-delay, making this an effective method to reduce impact.

2. Rate Limiting at Server Level

Nginx rate limiting:

# Limit MJ12bot to 60 requests per minute
limit_req_zone $http_user_agent zone=mj12:10m rate=60r/m;

if ($http_user_agent ~* "MJ12bot") {
    set $limit_mj12 1;
}

if ($limit_mj12 = 1) {
    limit_req zone=mj12 burst=10;
}

3. Contact Majestic Support

For persistent issues:

• Email: support@majestic.com
• Request reduced crawl rate for your domain
• Report excessive crawling behavior
• Discuss specific concerns

Majestic is generally responsive to crawl rate requests.

Detecting MJ12bot

Check Server Logs

# Find MJ12bot requests
grep -i "mj12bot" /var/log/apache2/access.log

# Count requests today
grep -i "mj12bot" access.log | grep "$(date +%d/%b/%Y)" | wc -l

# Most crawled pages
grep -i "mj12bot" access.log | awk '{print $7}' | sort | uniq -c | sort -rn | head -20

# Bandwidth consumed (approximate)
grep -i "mj12bot" access.log | awk '{sum += $10} END {print sum/1024/1024 " MB"}'

Verify Legitimacy

Verify using reverse DNS lookup:

host [IP address]
# Should resolve to *.mj12bot.com or Majestic's IP ranges

host [resolved hostname]
# Should return the original IP

Legitimate MJ12bot traffic comes from verified Majestic infrastructure.

Monitor Performance Impact

Watch for:

• Increased server load during crawls
• Bandwidth spikes
• Slower response times for regular users
• High concurrent connections

Understanding Majestic’s Metrics

If you allow MJ12bot, your site will be included in Majestic’s metrics:

Trust Flow (TF)

• Measures link quality
• Based on proximity to trusted seed sites
• Scale: 0-100
• Higher is better

Citation Flow (CF)

• Measures link quantity
• Based on number of links
• Scale: 0-100
• Higher indicates more links

Trust Flow / Citation Flow Ratio

• TF/CF ratio indicates natural vs. spammy links
• Good ratio: TF close to CF
• Bad ratio: CF much higher than TF (spam indicator)

Topical Trust Flow

• Categorizes site by topic
• Shows which categories link to you
• Helps understand topical authority

Comparison with Other SEO Bots

Benefits of Allowing MJ12bot

For Your Analysis:

• Track your backlink growth
• Monitor Trust Flow and Citation Flow
• Analyze competitor link profiles
• Identify link opportunities
• Historical link data access

For Visibility:

• Appear in Majestic’s index
• Be discoverable by SEO professionals
• Showcase your link authority
• Demonstrate Trust Flow metrics

For SEO Work:

• Validate your link building efforts
• See which links Majestic discovers
• Monitor link profile health
• Track topical relevance

When to Block MJ12bot

Server Performance Issues:

If you notice:

• Slow site performance during MJ12bot crawls
• High server load
• Bandwidth limits being reached
• Impacts on user experience

Business Reasons:

• Highly competitive niche
• Want to hide link building strategy
• Don’t use Majestic tools
• Prefer privacy over visibility
• Limited server capacity

Privacy Concerns:

• Don’t want competitors analyzing your links
• Building private link networks (PBN)
• Testing new link strategies
• Proprietary SEO approaches

Alternatives to Complete Blocking

1. Selective Blocking

User-agent: MJ12bot
Disallow: /admin/
Disallow: /private/
Disallow: /staging/
Disallow: /api/
Allow: /blog/
Allow: /

2. Time-Based Access

Allow crawling only during off-peak hours using server rules.

3. Aggressive Rate Limiting

User-agent: MJ12bot
Crawl-delay: 60

This significantly reduces impact while still allowing indexing.

4. Partial Content Access

Block resource-heavy sections while allowing blog/content areas.

Common Issues and Solutions

Issue 1: Excessive Server Load

Symptoms: High CPU usage, slow response times Solutions:

• Implement crawl-delay of 30-60 seconds
• Use server-level rate limiting
• Contact Majestic to reduce crawl rate
• Block temporarily during peak hours

Issue 2: Bandwidth Overuse

Symptoms: High bandwidth consumption, costs increasing Solutions:

• Block large files (PDFs, videos, downloads)
• Limit crawl rate via robots.txt
• Monitor and set bandwidth alerts
• Consider CDN for static resources

Issue 3: Database Load

Symptoms: Database slow during crawls Solutions:

• Cache dynamic content for bots
• Optimize database queries
• Implement static page generation
• Rate limit database-heavy pages

Issue 4: Log File Bloat

Symptoms: Massive log files, disk space issues Solutions:

• Implement log rotation
• Filter MJ12bot to separate log file
• Use log aggregation tools
• Compress old logs

Best Practices

If You Allow MJ12bot:

1. Monitor regularly: Check crawl impact weekly
2. Set reasonable limits: Use crawl-delay
3. Optimize for crawlers: Fast, cacheable responses
4. Update robots.txt: Block unnecessary sections
5. Track metrics: Monitor your Majestic Trust Flow

If You Block MJ12bot:

1. Complete blocking: Use both robots.txt and server-level
2. Verify blocking: Check logs to confirm
3. Document decision: Note why you blocked it
4. Review periodically: Reassess if needs change
5. Consider alternatives: Other link analysis tools

Industry Perspective

Who Typically Allows MJ12bot:

• SEO agencies and consultants
• Link building services
• Content marketing sites
• Sites with strong server infrastructure
• Companies using Majestic tools

Who Typically Blocks MJ12bot:

• Small sites with limited resources
• High-traffic sites conserving bandwidth
• Competitive niches (finance, gambling, health)
• Private blog networks (PBNs)
• Sites experiencing performance issues

Technical Details

Crawl Behavior:

• Respects robots.txt directives
• Follows most links it encounters
• Crawls JavaScript-rendered content
• Handles redirects properly
• Respects canonical tags
• Does not execute forms or POST requests

IP Ranges:

MJ12bot operates from multiple IP addresses:

• Regularly updated IP ranges
• Distributed globally
• Can verify via reverse DNS
• Listed on Majestic’s website

Politeness:

• Honors crawl-delay
• Backs off on errors
• Limits concurrent connections
• Generally follows best practices
• But: Very high volume overall

Future Considerations

As SEO and link analysis evolve:

• MJ12bot may incorporate AI-powered analysis
• More sophisticated crawling patterns
• Better resource optimization
• Enhanced respect for site preferences
• Potential integration with other data sources

Conclusion

MJ12bot is a legitimate, highly active crawler that powers Majestic’s industry-leading backlink analysis tools. It’s one of the most aggressive crawlers you’ll encounter, which presents a trade-off:

Allow it if:

• You value comprehensive backlink data
• You use Majestic tools
• Your infrastructure can handle the load
• You want maximum visibility in SEO tools

Block it if:

• Server resources are limited
• You’re experiencing performance issues
• You want to maintain competitive privacy
• You don’t benefit from link analysis tool visibility

Many sites choose a middle approach: allowing MJ12bot but implementing aggressive crawl-delay settings (30-60 seconds) to balance backlink indexing with server resource management. Monitor your server logs to assess the actual impact on your specific site and adjust accordingly.

Test MJ12bot Access to Your Site

Use our SEO Tools Bot Checker to verify if MJ12bot can access your website. This free tool tests robots.txt rules and actual bot access for Majestic and other SEO analytics crawlers.

Related SEO Tool Bots:

• AhrefsBot - Ahrefs backlink and SEO crawler
• SemrushBot - SEMrush competitive analysis bot
• DotBot - Moz domain authority crawler

For comprehensive bot testing across all categories, explore our free bot detection tools.