Plus Sign UTM Inconsistency: Why + Shows as Space Sometimes

Your campaign name is "google+ads" but GA4 sometimes shows "google ads" (with space), sometimes "google+ads" (with plus).

Plus signs in URLs behave unpredictably. Here's why and how to fix it.

The Problem

URL: ?utm_campaign=google+ads

GA4 shows inconsistently:
- Session 1: "google ads" (+ decoded as space)
- Session 2: "google+ads" (+ kept as +)
- Session 3: "google  ads" (double space)

One campaign, three different values

Plus signs have dual meaning in URLs, causing inconsistent decoding.

Why + Is Ambiguous

Historical Context

In URLs, + can mean two different things:

1. In query strings: Space character (legacy encoding)

   ?search=hello+world → "hello world"
   

2. As literal +: The actual plus symbol

   ?tech=C++ → "C++"
   

Problem: Browsers and analytics platforms decode + inconsistently.

Real Example

Company: Digital marketing agency Campaign: "Google+Bing Ads" Budget: $30,000 URL: ?utm_campaign=google+bing

GA4 Results:

Browser          | Campaign Value Shown
-----------------|---------------------
Chrome Desktop   | "google bing" (space)
Firefox          | "google bing" (space)
Safari iOS       | "google+bing" (kept +)
Android Chrome   | "google bing" (space)

Impact:

• Same campaign appears as 2 different values in GA4
• Data fragmented between "google bing" and "google+bing"
• Could not get accurate performance totals
• Reports showed two separate campaigns

$30,000 attribution split across inconsistent values.

When + Gets Decoded as Space

// Test browser behavior
const url = 'https://site.com?utm_campaign=google+bing';
const params = new URLSearchParams(url.split('?')[1]);
console.log(params.get('utm_campaign'));
// Most browsers output: "google bing" (space)
 
// + is decoded as space in query string context

When + Stays as +

Some contexts preserve +:
- URL displayed in address bar (before decoding)
- Some mobile browsers (platform-dependent)
- Certain email click tracking systems
- URL shorteners (depends on implementation)

Result: Inconsistent GA4 values

The Fix

Option 1: Encode + as %2B (Recommended)

❌ AMBIGUOUS:
utm_campaign=google+bing

✅ EXPLICIT:
utm_campaign=google%2Bbing

GA4 always shows: "google+bing"

Option 2: Use Different Separator

❌ AMBIGUOUS:
utm_campaign=google+bing

✅ CLEAR:
utm_campaign=google-bing
utm_campaign=google_bing
utm_campaign=googlebing

No encoding ambiguity

Option 3: Spell Out "plus"

❌ AMBIGUOUS:
utm_campaign=C++

✅ CLEAR:
utm_campaign=c-plus-plus
utm_campaign=cplusplus

Readable, no encoding issues

Encoding Script

function fixPlusSign(value) {
    // Check if value contains +
    if (value.includes('+')) {
        console.warn(`Value contains + which may decode inconsistently: "${"{"}{"{"}value{"}"}{"}"}}"`);
 
        // Option 1: Encode + as %2B
        const encoded = value.replace(/\+/g, '%2B');
        console.log(`Encoded version: "${"{"}{"{"}encoded{"}"}{"}"}}"`);
 
        // Option 2: Replace with hyphen
        const hyphenated = value.replace(/\+/g, '-');
        console.log(`Hyphenated version: "${"{"}{"{"}hyphenated{"}"}{"}"}}"`);
 
        return encoded; // Return encoded by default
    }
 
    return value;
}
 
// Usage
const campaign = 'google+bing';
const fixed = fixPlusSign(campaign);
console.log(fixed);
// google%2Bbing

Detection Script

function detectPlusSignIssues(url) {
    const params = new URL(url).searchParams;
    const issues = [];
 
    ['utm_source', 'utm_medium', 'utm_campaign', 'utm_content', 'utm_term'].forEach(key => {
        const value = params.get(key);
        const rawQuery = url.split('?')[1] || '';
        const paramPattern = new RegExp(`${"{"}{"{"}key{"}"}{"}"}}=([^&]*)`);
        const match = rawQuery.match(paramPattern);
 
        if (match && match[1].includes('+') && !match[1].includes('%2B')) {
            issues.push({
                parameter: key,
                rawValue: match[1],
                decodedValue: value,
                warning: '+ may decode inconsistently across browsers',
                fix: match[1].replace(/\+/g, '%2B')
            });
        }
    });
 
    return {
        hasIssues: issues.length > 0,
        issues
    };
}
 
// Usage
const url = 'site.com?utm_campaign=google+bing';
const result = detectPlusSignIssues(url);
 
if (result.hasIssues) {
    console.log('⚠️  Plus sign issues detected:');
    result.issues.forEach(issue => {
        console.log(`  ${issue.parameter}: "${issue.rawValue}" → fix: "${issue.fix}"`);
    });
}

Testing Across Browsers

// Test script to run in different browsers
function testPlusDecoding() {
    const testUrl = 'https://test.com?param=a+b';
    const url = new URL(testUrl);
    const value = url.searchParams.get('param');
 
    console.log('Browser:', navigator.userAgent);
    console.log('URL:', testUrl);
    console.log('Decoded value:', value);
    console.log('Is space?', value === 'a b');
    console.log('Is plus?', value === 'a+b');
}
 
// Run in:
// - Chrome Desktop
// - Firefox
// - Safari Desktop
// - Safari iOS
// - Chrome Android
 
// Compare results to see inconsistency

Platform Behavior

Universal fix: Encode + as %2B when you mean literal plus sign.

Common Scenarios

Scenario 1: Product Names

Product: C++ Programming

❌ INCONSISTENT:
utm_content=C++

✅ CONSISTENT:
utm_content=C%2B%2B
utm_content=Cplusplus
utm_content=cpp

Scenario 2: Brand Names

Brand: Google+

❌ INCONSISTENT:
utm_source=google+

✅ CONSISTENT:
utm_source=google%2B
utm_source=googleplus

Scenario 3: Mathematical Expressions

Offer: 1+1=2

❌ INCONSISTENT:
utm_campaign=1+1=2

✅ CONSISTENT:
utm_campaign=1%2B1%3D2
utm_campaign=one-plus-one
utm_campaign=2for1

Prevention Checklist

Before launching campaigns with + in values:

✅ Identify all + symbols in parameter values
✅ Decide: Encode (%2B) or replace (-, _, remove)?
✅ Test URL in multiple browsers
✅ Check GA4 Real-Time after clicking
✅ Verify consistent decoding
✅ Document decision for team

FAQ

Is + ever safe to use in UTM parameters?

Not reliably. Encode as %2B if you need literal +, or use alternative separator.

Why does + sometimes work?

Some platforms preserve + in certain contexts, but behavior is inconsistent. Don't rely on it.

Should I use + or %20 for spaces?

Use %20 or underscores. + for spaces is legacy and can be ambiguous.

What if my campaign already launched with +?

Fix immediately. Update all placements. Use %2B or alternative separator going forward.

Conclusion

Plus signs in UTM parameters decode inconsistently: sometimes as space, sometimes as +.

Fixes:

1. Encode: + → %2B (reliable across all platforms)
2. Replace: + → - or _ (simpler, no encoding)
3. Remove: google+bing → googlebing

Never use unencoded + in UTM values. Always encode as %2B or use alternatives.

❌ utm_campaign=google+bing
✅ utm_campaign=google%2Bbing
✅ utm_campaign=google-bing

Technical Reference: Plus Sign in Value Validation Rule