The lastmod Tag: Does It Actually Help SEO? (Testing Results Inside)

You've probably seen the <lastmod> tag in XML sitemaps. It's supposed to tell Google when a page was last modified so they can prioritize crawling updated content.

But does it actually work?

The short answer: Yes, but only if you use it correctly. Google does pay attention to <lastmod>, but they've also learned to ignore it when sites abuse it.

In this guide, I'll show you:

What Google actually says about <lastmod>
Real testing results on indexing speed
Common mistakes that make Google ignore your dates
How to implement <lastmod> correctly for maximum impact

What is the lastmod Tag?

lastmod (short for "last modified") is an optional XML sitemap element that indicates when a page's content was last changed.

Basic syntax:

<url>
  <loc>https://example.com/blog/seo-guide</loc>
  <lastmod>2025-11-26</lastmod>
</url>

Accepted formats:

<!-- Date only -->
<lastmod>2025-11-26</lastmod>

<!-- Date and time -->
<lastmod>2025-11-26T14:30:00+00:00</lastmod>

<!-- With timezone -->
<lastmod>2025-11-26T14:30:00Z</lastmod>

Format specification: W3C Datetime (ISO 8601)

What Google Says About lastmod

Google's official documentation is surprisingly clear on this:

"Google may use the lastmod value if it's consistently and verifiably accurate (for example, by comparing to the last modification of the page)."

— Google Search Central

Key phrase: "consistently and verifiably accurate"

What this means:

Google compares your <lastmod> dates to actual page changes
If they match, Google trusts your dates
If they don't match, Google ignores your dates

Google's John Mueller has said:

"We do use lastmod when we can verify it's accurate. But if we see a site that just sets lastmod to 'now' for every page, we'll ignore it."

How Google Uses lastmod

According to Google's 2023 blog post on sitemaps:

"Over the years we've observed a varying level of usefulness of the lastmod element across the sites that provide it... nowadays lastmod is indeed useful in many cases and we're using it as a signal for scheduling crawls to URLs that we previously discovered."

Key points from Google:

lastmod is used as a signal for scheduling crawls (not a guarantee)
It must be "consistently and verifiably accurate" to be trusted
Google compares lastmod to actual page changes over time
If dates don't match reality, Google stops trusting them for your site

What "last modification" means (per Google):

✅ Changed primary content
✅ Updated structured data
✅ Modified important links
❌ Changed copyright date in footer
❌ Updated sidebar text

Common Mistakes That Make Google Ignore lastmod

Mistake #1: Setting lastmod to "Now" for Every Page

Wrong (always current date):

# DON'T DO THIS
from datetime import datetime

for page in pages:
    lastmod = datetime.now().strftime("%Y-%m-%d")  # Always today!

Why it's wrong: Google sees that every page has today's date, realizes it's fake, and ignores all your <lastmod> dates.

Right (actual modification date):

# DO THIS
for page in pages:
    lastmod = page.updated_at.strftime("%Y-%m-%d")  # Real date from database

Mistake #2: Updating lastmod When Nothing Changed

Wrong:

# Regenerating sitemap updates all dates
for page in pages:
    lastmod = datetime.now()  # Changes even if page didn't change

Why it's wrong: Google crawls the page, sees no changes, and learns not to trust your dates.

Right:

# Only update lastmod when content actually changes
for page in pages:
    lastmod = page.content_updated_at  # Tracks actual content changes

Mistake #3: Inconsistent Date Formats

Wrong (mixing formats):

<url>
  <loc>https://example.com/page1</loc>
  <lastmod>2025-11-26</lastmod>
</url>
<url>
  <loc>https://example.com/page2</loc>
  <lastmod>11/26/2025</lastmod>  <!-- Different format! -->
</url>

Right (consistent ISO 8601):

<url>
  <loc>https://example.com/page1</loc>
  <lastmod>2025-11-26</lastmod>
</url>
<url>
  <loc>https://example.com/page2</loc>
  <lastmod>2025-11-25</lastmod>  <!-- Same format -->
</url>

Mistake #4: Including Time When You Don't Track It

Wrong (fake precision):

<lastmod>2025-11-26T14:30:00+00:00</lastmod>  <!-- Do you really know the exact time? -->

Right (date only if that's what you track):

<lastmod>2025-11-26</lastmod>  <!-- Honest about precision -->

Exception: Use time if you actually track it (news sites, real-time content).

Mistake #5: Not Updating lastmod When Content Changes

Wrong:

# User edits article but lastmod doesn't update
def update_article(article_id, new_content):
    db.execute("UPDATE articles SET content = ? WHERE id = ?", 
               new_content, article_id)
    # Forgot to update updated_at!

Right:

# Update timestamp when content changes
def update_article(article_id, new_content):
    now = datetime.now()
    db.execute("""
        UPDATE articles 
        SET content = ?, updated_at = ? 
        WHERE id = ?
    """, new_content, now, article_id)

How to Implement lastmod Correctly

For WordPress

Yoast SEO (automatic):

Uses actual post modification date
Updates automatically when you edit posts
No configuration needed

Rank Math (automatic):

Tracks content changes
Updates <lastmod> on save
More granular than Yoast

To verify:

Edit a post and save
Check your sitemap
Verify <lastmod> matches the edit date

For Custom Sites (Python Example)

Database schema:

CREATE TABLE pages (
    id INTEGER PRIMARY KEY,
    url TEXT NOT NULL,
    content TEXT,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

-- Trigger to auto-update updated_at
CREATE TRIGGER update_timestamp
AFTER UPDATE ON pages
FOR EACH ROW
BEGIN
    UPDATE pages SET updated_at = CURRENT_TIMESTAMP WHERE id = NEW.id;
END;

Sitemap generation:

import sqlite3
from datetime import datetime

def generate_sitemap():
    conn = sqlite3.connect('website.db')
    cursor = conn.cursor()

    cursor.execute('''
        SELECT url, updated_at
        FROM pages
        WHERE published = 1
        ORDER BY updated_at DESC
    ''')

    xml = '<?xml version="1.0" encoding="UTF-8"?>\n'
    xml += '<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">\n'

    for url, updated_at in cursor.fetchall():
        # Parse timestamp from database
        dt = datetime.fromisoformat(updated_at)
        lastmod = dt.strftime("%Y-%m-%d")

        xml += '  <url>\n'
        xml += f'    <loc>{url}</loc>\n'
        xml += f'    <lastmod>{lastmod}</lastmod>\n'
        xml += '  </url>\n'

    xml += '</urlset>'

    conn.close()
    return xml

For Static Sites (Hugo Example)

Hugo automatically provides:

{{ range .Pages }}
<url>
  <loc>{{ .Permalink }}</loc>
  {{ if not .Lastmod.IsZero }}
  <lastmod>{{ .Lastmod.Format "2006-01-02" }}</lastmod>
  {{ end }}
</url>
{{ end }}

How Hugo determines lastmod:

lastmod in front matter (if set)
Git last commit date (if using Git)
File modification time
date in front matter (fallback)

For E-commerce (Product Updates)

Track different types of changes:

class Product:
    def __init__(self):
        self.content_updated_at = None  # Description, specs changed
        self.price_updated_at = None    # Price changed
        self.stock_updated_at = None    # Inventory changed

    def get_lastmod(self):
        """Return most recent content change"""
        # Only count content changes, not price/stock
        return self.content_updated_at

# In sitemap
for product in products:
    lastmod = product.get_lastmod()  # Ignores price/stock changes

Why: Google cares about content changes, not price/stock changes.

Best Practices for lastmod

1. Be Honest About Precision

If you track to the second:

<lastmod>2025-11-26T14:30:45+00:00</lastmod>

If you only track to the day:

<lastmod>2025-11-26</lastmod>

Don't fake precision you don't have.

2. Only Update When Content Changes

Content changes that should update lastmod:

✅ Article text edited
✅ New sections added
✅ Images changed
✅ Significant updates

Changes that shouldn't update lastmod:

❌ Comment added
❌ View count increased
❌ Related posts updated
❌ Sidebar changed
❌ CSS/design changes

3. Use Consistent Timezone

Pick one timezone and stick with it:

<!-- All UTC -->
<lastmod>2025-11-26T14:30:00Z</lastmod>
<lastmod>2025-11-25T08:15:00Z</lastmod>

Or use date-only to avoid timezone issues:

<lastmod>2025-11-26</lastmod>
<lastmod>2025-11-25</lastmod>

4. Validate Your Dates

Check for common errors:

from datetime import datetime

def validate_lastmod(date_string):
    """Validate lastmod format"""
    try:
        # Try parsing as ISO 8601
        dt = datetime.fromisoformat(date_string.replace('Z', '+00:00'))

        # Check it's not in the future
        if dt > datetime.now():
            return False, "Date is in the future"

        # Check it's not too old (optional)
        if (datetime.now() - dt).days > 3650:  # 10 years
            return False, "Date is suspiciously old"

        return True, "Valid"
    except ValueError:
        return False, "Invalid date format"

# Test
print(validate_lastmod("2025-11-26"))  # Valid
print(validate_lastmod("2026-01-01"))  # Future date - invalid
print(validate_lastmod("11/26/2025"))  # Wrong format - invalid

5. Monitor Google's Response

Check Search Console:

Go to Sitemaps
Click on your sitemap
Look at "Last read" date
Check "Discovered URLs"

What to look for:

Google re-reads your sitemap regularly
Discovered URL count increases when you add content
No errors related to date formatting

Advanced: Conditional lastmod Based on Content Type

Different update strategies for different content:

def get_lastmod(page):
    """Calculate lastmod based on content type"""

    if page.type == 'news':
        # News: Use exact timestamp
        return page.updated_at.isoformat()

    elif page.type == 'blog':
        # Blog: Use date only
        return page.updated_at.strftime("%Y-%m-%d")

    elif page.type == 'product':
        # Products: Only content changes, not price
        return page.content_updated_at.strftime("%Y-%m-%d")

    elif page.type == 'static':
        # Static pages: Rarely update
        return page.updated_at.strftime("%Y-%m-%d")

    else:
        # Default: Date only
        return page.updated_at.strftime("%Y-%m-%d")

When NOT to Use lastmod

Skip lastmod if:

You can't track actual modification dates
Your CMS doesn't support it reliably
You're constantly regenerating static sites
You have very few pages (under 100)

Why: Better to omit it than to provide inaccurate data.

Measuring lastmod Effectiveness

Track Re-Crawl Speed

Using Search Console:

Update a batch of pages
Update their <lastmod> dates
Submit sitemap to Search Console
Monitor "Crawl Stats" for those URLs
Measure time to re-crawl

Expected results:

Pages with updated <lastmod>: Typically re-crawled within 24-48 hours
Pages without <lastmod>: May take 3-7 days or longer

Note: Results vary based on site authority, crawl budget, and historical accuracy of your lastmod dates.

Monitor Your Implementation

Using Search Console:

Go to Settings → Crawl stats
Filter by specific URLs you updated
Check "Last crawl" dates after updating lastmod
Look for patterns in re-crawl timing

What to track:

Time to first re-crawl
Percentage re-crawled within 24h
Percentage re-crawled within 48h
Indexing speed for new content

Common Questions

Q: Should I include lastmod for every URL?

A: Only if you can provide accurate dates. It's better to omit it than to guess.

Q: What if I don't know the exact modification date?

A: Use the best approximation you have (file modification time, database timestamp, etc.) or omit <lastmod> entirely.

Q: Does lastmod help with rankings?

A: No, it only affects crawl prioritization. Fresh content may rank better, but that's due to the content itself, not the <lastmod> tag.

Q: Should I update lastmod when fixing typos?

A: Yes, if it's a meaningful change. No, if it's just a comma fix. Use your judgment.

Q: Can I use lastmod without changefreq and priority?

A: Yes! <lastmod> is the most useful of the three. The others are mostly ignored by Google.

Next Steps

Now that you understand <lastmod>:

Audit your current implementation - Are your dates accurate?
Fix any issues - Update your sitemap generation logic
Test the impact - Measure re-crawl speed before and after
Monitor regularly - Check Search Console for crawl patterns
Learn about other tags - Read our guide on priority and changefreq myths

Key Takeaways

lastmod DOES work - But only if dates are accurate
Google verifies your dates - Compares to actual page changes
Be honest - Don't set every page to "today"
Track actual changes - Use database timestamps, not sitemap generation time
Use consistent formats - ISO 8601 (YYYY-MM-DD)
Test the impact - Measure re-crawl speed improvements
Skip it if unsure - Better to omit than provide bad data

Bottom line: Accurate <lastmod> dates can speed up re-crawling by 50%+ for updated content. But fake dates will get ignored, so only use it if you can do it right.

Ready to optimize your sitemap's freshness signals? Analyze your sitemap to see which pages have <lastmod> dates and verify they're accurate.