Ampersand Breaking UTM Tracking: Fix & Symbol in Parameter Values

Your campaign name is "save & win" but GA4 only shows "save". Everything after the & is missing.

Unencoded ampersands break parameter parsing. Here's the 60-second fix.

The Problem

❌ BROKEN:
?utm_campaign=save&win

Browser parses as:
utm_campaign = "save"
win = "" (new parameter with no value)

GA4 receives: campaign = "save"
Missing: "& win"

The & symbol is a reserved URL character. It separates parameters.

When you use & in a parameter value without encoding, the browser thinks you're starting a new parameter.

Why It Happens

Ampersand (&) is the parameter separator in URLs:

✅ CORRECT USAGE (separating parameters):
?utm_source=facebook&utm_medium=cpc&utm_campaign=spring
                    ↑              ↑
             Parameter separators

But when & appears INSIDE a value:

❌ WRONG (& in value, not encoded):
?utm_campaign=save&win&utm_medium=cpc
              ↑   ↑
         Intended as part of campaign name
         Parsed as parameter separator

Result:
- utm_campaign = "save"
- win = ""
- utm_medium = "cpc"

Real Example

Company: E-commerce retailer Campaign: "Buy 1 & Get 1 Free" promotion Budget: $25,000 Facebook ads URL: ?utm_campaign=buy1&get1free

Result in GA4:

• Campaign name: "buy1"
• Everything after & lost

Impact:

• Could not identify "Buy 1 & Get 1" campaign in reports
• Data split: some sessions showed "buy1", some showed nothing
• $25,000 spend with truncated attribution
• Could not measure actual promo performance

Encoding the & would have preserved full tracking.

The Fix

Option 1: Encode as %26

❌ BEFORE:
?utm_campaign=save&win

✅ AFTER:
?utm_campaign=save%26win

GA4 shows: "save&win" (decoded automatically)

Option 2: Replace with "and"

❌ BEFORE:
?utm_campaign=save&win

✅ AFTER:
?utm_campaign=save-and-win

GA4 shows: "save-and-win"

Option 3: Remove Ampersand

❌ BEFORE:
?utm_campaign=buy1&get1

✅ AFTER:
?utm_campaign=buy1get1

GA4 shows: "buy1get1"

Quick Encoding Script

function encodeUtmValue(value) {
    // Encode all special characters including &
    return encodeURIComponent(value);
}
 
// Usage
const campaign = "save & win";
const encoded = encodeUtmValue(campaign);
console.log(encoded);
// Output: save%20%26%20win
//              ↑  ↑
//          space  ampersand
 
// Build full URL
const url = `https://site.com?utm_campaign=${"{"}{"{"}encoded{"}"}{"}"}}`;
console.log(url);
// https://site.com?utm_campaign=save%20%26%20win
 
// GA4 receives: "save & win" (automatically decoded)

How Browsers Parse Ampersands

Example URL:
https://site.com?utm_campaign=save&win&utm_medium=cpc

Browser interpretation:
Parameter 1: utm_campaign = "save"
Parameter 2: win = "" (no value provided)
Parameter 3: utm_medium = "cpc"

URLSearchParams output:
utm_campaign: "save"
win: ""
utm_medium: "cpc"

GA4 receives:
Campaign: "save"
Medium: "cpc"
(Everything between & symbols is lost or misinterpreted)

Detection Script

function detectUnencodedAmpersand(url) {
    const params = new URL(url).searchParams;
    const issues = [];
 
    params.forEach((value, key) => {
        // Check if value contains unencoded &
        // (encoded & appears as %26 in raw query string)
        const rawQuery = url.split('?')[1] || '';
        const paramPattern = new RegExp(`${"{"}{"{"}key{"}"}{"}"}}=([^&]*)`);
        const match = rawQuery.match(paramPattern);
 
        if (match) {
            const rawValue = match[1];
            // If raw value contains & but not %26, it's unencoded
            if (rawValue.includes('&') && !rawValue.includes('%26')) {
                issues.push({
                    parameter: key,
                    value: value,
                    problem: 'Contains unencoded ampersand',
                    fix: `Encode as ${encodeURIComponent(value)}`
                });
            }
        }
    });
 
    return issues;
}
 
// Usage
const url = 'site.com?utm_campaign=save&win';
console.log(detectUnencodedAmpersand(url));
// [{ parameter: 'utm_campaign', value: 'save', problem: 'Contains unencoded ampersand', ... }]

Testing After Fix

Step 1: Check URL Structure

✅ CORRECT:
https://site.com?utm_campaign=save%26win&utm_medium=cpc
                             ↑   ↑
                         Encoded &

Each %26 in URL = one & in the final value

Step 2: Test in Browser

1. Visit URL: https://site.com?utm_campaign=save%26win
2. Open browser console
3. Run: new URL(location.href).searchParams.get('utm_campaign')
4. Should output: "save&win" (decoded)

Step 3: Verify in GA4

1. Visit corrected URL
2. Open GA4 → Realtime
3. Check "Traffic acquisition"
4. Campaign should show complete value: "save&win"

Common Ampersand Scenarios

Scenario 1: Company Name with &

❌ WRONG:
utm_source=johnson&johnson

✅ RIGHT:
utm_source=johnson%26johnson

GA4 shows: "johnson&johnson"

Scenario 2: Product Names

❌ WRONG:
utm_content=shoes&boots

✅ RIGHT:
utm_content=shoes%26boots

GA4 shows: "shoes&boots"

Scenario 3: Promotional Copy

❌ WRONG:
utm_campaign=save-big&act-fast

✅ RIGHT:
utm_campaign=save-big%26act-fast

GA4 shows: "save-big&act-fast"

Platform-Specific Handling

Google Ads

Value Tracking Template:
`{"{"}{"{"}lpurl{"}"}{"}"}}`?utm_campaign=buy1%26get1free&gclid=`{"{"}{"{"}gclid{"}"}{"}"}}`
                         ↑
                    Pre-encoded & in campaign name

Facebook Ads

URL Parameters field:
utm_source=facebook&utm_campaign=spring%26summer
                                     ↑
                               Encoded &

Email Platforms

<!-- Pre-encode in template -->
<a href="https://site.com?utm_campaign=save%26win&utm_source=email">
    Click Here
</a>
 
<!-- Platform's click tracking preserves %26 -->

Prevention Checklist

Before launching campaigns:

✅ Scan all UTM values for & symbols
✅ Replace with:
   - %26 (encoded, preserves &)
   - "and" (readable alternative)
   - Remove (if not needed)
✅ Use encodeURIComponent() for automation
✅ Test URL in browser console
✅ Verify in GA4 Real-Time

FAQ

Why does & break URLs?

& is reserved as the parameter separator. Using it in values without encoding confuses URL parsers.

Should I always encode & to %26?

Yes, if you want the & to appear in GA4. Alternative: replace with "and" or remove.

What if my platform auto-encodes?

Test it. Some platforms encode, some don't. Always verify the final URL received by users.

Can I use & in the base URL?

Yes. & is only problematic when used INSIDE parameter values. Between parameters, & is correct.

✅ CORRECT:
?param1=value1&param2=value2
              ↑
         & separating parameters (correct)

❌ WRONG:
?param1=value&value
            ↑
         & inside value (must encode as %26)

Conclusion

Unencoded & in UTM values breaks parameter parsing. Fix: Encode as %26.

❌ utm_campaign=save&win
✅ utm_campaign=save%26win
✅ utm_campaign=save-and-win

Use encodeURIComponent() to automatically encode all special characters including &.

Technical Reference: Ampersand Not Encoded Validation Rule