UTMGuard

Fix URL Encoding Errors: Complete Troubleshooting Guide

UTMGuard Team
••8 min read•troubleshooting

GA4 shows your campaign as "spring%20sale" instead of "spring sale."

Or parameters are truncated. Or special characters appear as gibberish.

Every URL encoding error has a specific fix. Here's your troubleshooting guide.

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Common Encoding Errors

Error 1: Literal %20 in Reports

GA4 shows: spring%20sale%20202 4
Expected:  spring sale 2024

Cause: Double-encoded URL

Error 2: Truncated Parameters

GA4 shows: spring
Expected:  spring sale 2024

Cause: Unencoded spaces

Error 3: Missing Parameters

GA4 shows: utm_source only
Expected:  utm_source, utm_medium, utm_campaign

Cause: Unencoded & symbol

Error 4: Corrupted Characters

GA4 shows: spring%20sale%26save
Expected:  spring sale & save

Cause: Mixed encoding levels

😰 Is this your only tracking issue?

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• 94% of sites have UTM errors

• Average: $8,400/month in wasted ad spend

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Diagnostic Process

Step 1: Check Browser Address Bar (30 seconds)

Visit the URL and look at the address bar:

✅ CORRECT (single-encoded):
https://site.com?utm_campaign=spring%20sale
Browser displays: spring sale (decoded for readability)

❌ WRONG (double-encoded):
https://site.com?utm_campaign=spring%2520sale
Browser displays: spring%20sale (literal %20)

Step 2: Check GA4 Reports (30 seconds)

Open GA4 → Reports → Acquisition → Traffic acquisition

If you see:           Problem is:
----------------      ------------------
"spring%20sale"       Double-encoding
"spring"              Unencoded spaces (truncated)
"spring%26win"        Unencoded ampersand
"spring’sale"       Character encoding mismatch

Step 3: Inspect URL Structure (60 seconds)

Paste URL into text editor and examine:

// Check for common issues
function diagnoseUrl(url) {
    const issues = [];
 
    // Issue 1: Double encoding
    if (url.includes('%25')) {
        issues.push({
            problem: 'Double-encoding detected',
            indicator: '%25 (encoded %)',
            fix: 'Decode once before using'
        });
    }
 
    // Issue 2: Unencoded spaces
    const queryString = url.split('?')[1] || '';
    if (queryString.includes(' ')) {
        issues.push({
            problem: 'Unencoded spaces',
            indicator: 'Literal space character',
            fix: 'Replace spaces with %20'
        });
    }
 
    // Issue 3: Unencoded ampersand
    const value = url.match(/utm_campaign=([^&]*)/)?.[1] || '';
    if (value.includes('&') && !value.includes('%26')) {
        issues.push({
            problem: 'Unencoded ampersand in value',
            indicator: '& not encoded as %26',
            fix: 'Encode & as %26 in parameter values'
        });
    }
 
    return issues;
}

Fix: Double-Encoding

Symptom

GA4 campaign: "spring%20sale"
Expected:     "spring sale"

Solution

Decode URL once before using:

// ❌ WRONG: Encoding already-encoded URL
const url = 'site.com?utm_campaign=spring%20sale';
const encoded = encodeURIComponent(url);
// Result: spring%2520sale (double-encoded)
 
// ✅ RIGHT: Check if already encoded
function safeEncode(value) {
    // Decode first (in case already encoded)
    const decoded = decodeURIComponent(value);
    // Then encode
    return encodeURIComponent(decoded);
}
 
const fixed = safeEncode('spring%20sale');
// Result: spring%20sale (correctly single-encoded)

Testing

// Test URL decoding
const url = 'site.com?utm_campaign=spring%2520sale';
const param = new URL(url).searchParams.get('utm_campaign');
console.log(param);
// If shows "spring%20sale", URL is double-encoded
 
// Fix
const decoded = decodeURIComponent(param);
console.log(decoded);
// Should show: "spring sale"

Fix: Unencoded Spaces

Symptom

GA4 campaign: "spring"
Expected:     "spring sale 2024"

Solution

Replace all spaces with %20:

// Manual fix
const broken = 'site.com?utm_campaign=spring sale 2024';
const fixed = broken.replace(/ /g, '%20');
// Result: site.com?utm_campaign=spring%20sale%202024
 
// Or use URLSearchParams (auto-encodes)
const params = new URLSearchParams();
params.append('utm_campaign', 'spring sale 2024');
const url = `site.com?${params.toString()}`;
// Result: site.com?utm_campaign=spring+sale+2024
// Note: + is valid encoding for spaces in query strings

Fix: Unencoded Special Characters

Symptom

GA4 shows incomplete data
Parameters after special character missing

Solution

Encode all special characters:

// Characters that MUST be encoded in URLs
const mustEncode = {
    ' ': '%20',  // Space
    '&': '%26',  // Ampersand
    '=': '%3D',  // Equals
    '?': '%3F',  // Question mark
    '#': '%23',  // Hash
    '+': '%2B',  // Plus (in values, not as space replacement)
    '%': '%25',  // Percent
    '/': '%2F',  // Forward slash (in values)
};
 
// Safe encoding function
function encodeUtmValue(value) {
    return encodeURIComponent(value);
}
 
// Usage
const campaign = 'save & win!';
const encoded = encodeUtmValue(campaign);
console.log(encoded);
// Output: save%20%26%20win!

Fix: Mixed Encoding Levels

Symptom

GA4 shows: "spring%20sale&save"
Expected:  "spring sale & save"

Problem: Space encoded, ampersand not encoded

Solution

Encode consistently:

// ❌ WRONG: Inconsistent encoding
const url = 'site.com?utm_campaign=spring%20sale&save';
//                                     ↑       ↑
//                              Encoded    Not encoded
 
// ✅ RIGHT: Encode entire value consistently
const value = 'spring sale & save';
const encoded = encodeURIComponent(value);
const url = `site.com?utm_campaign=${"{"}{"{"}encoded{"}"}{"}"}}`;
// Result: site.com?utm_campaign=spring%20sale%20%26%20save

Platform-Specific Fixes

Problem: Value Tracking template adds parameters
Fix: Ensure existing UTMs properly encoded before adding

// ✅ CORRECT
Final URL: https://site.com?utm_campaign=spring%20sale
Value Tracking: `{"{"}{"{"}lpurl{"}"}{"}"}}`?gclid=`{"{"}{"{"}gclid{"}"}{"}"}}`

Result: site.com?utm_campaign=spring%20sale&gclid=123

Facebook Ads

Problem: URL Parameters field in Ad Manager
Fix: Don't include ? in URL Parameters field

// ❌ WRONG
URL Parameters: ?utm_source=facebook&utm_medium=cpc

// ✅ RIGHT
URL Parameters: utm_source=facebook&utm_medium=cpc

Email Platforms

Problem: Click tracking double-encodes
Fix: Use single-encoded URLs, test delivery

// Test after sending
1. Send test email
2. Click link
3. Check browser address bar
4. Should show single-encoded parameters

Validation Script

function validateUrlEncoding(url) {
    const errors = [];
 
    // Extract query string
    const queryString = url.split('?')[1] || '';
 
    // Check 1: Unencoded spaces
    if (queryString.includes(' ')) {
        errors.push('Unencoded spaces detected');
    }
 
    // Check 2: Double encoding
    if (queryString.includes('%25')) {
        errors.push('Possible double-encoding (contains %25)');
    }
 
    // Check 3: Unencoded special characters
    const specialChars = ['&', '=', '?', '#'];
    const params = queryString.split('&');
    params.forEach(param => {
        const [, value] = param.split('=');
        if (value) {
            specialChars.forEach(char => {
                if (value.includes(char) && !value.includes(encodeURIComponent(char))) {
                    errors.push(`Unencoded ${"{"}{"{"}char{"}"}{"}"}} in parameter value`);
                }
            });
        }
    });
 
    // Check 4: Valid percent encoding
    const percentPattern = /%[0-9A-Fa-f]{2}/g;
    const invalidPercent = queryString.match(/%(?![0-9A-Fa-f]{2})/);
    if (invalidPercent) {
        errors.push('Invalid percent encoding detected');
    }
 
    return {
        valid: errors.length === 0,
        errors
    };
}
 
// Usage
const url = 'https://site.com?utm_campaign=spring sale';
const result = validateUrlEncoding(url);
console.log(result);
// { valid: false, errors: ['Unencoded spaces detected'] }

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FAQ

How do I know if my URL is double-encoded?

Check GA4 reports. If you see literal %20 or %26 characters, the URL is double-encoded.

Should I use %20 or + for spaces?

%20 works everywhere. + is valid in query strings but less reliable. Use %20 for consistency.

What if I've already launched with broken URLs?

Fix immediately, update all placements, and consider 301 redirects from broken to fixed URLs.

Can I decode URLs in GA4?

No. GA4 stores values as received. Fix the source URLs.

Conclusion

URL encoding errors corrupt UTM tracking. Systematic diagnosis and fixing restores data quality.

Quick Diagnostic:

  1. Check browser address bar for double-encoding
  2. Check GA4 for truncation or literal % codes
  3. Validate with encoding checker
  4. Fix at source and redeploy

Prevention: Use encodeURIComponent() for all parameter values.

Technical Reference: URL Encoding Issues Validation Rule