The complete 15-step workflow to validate, clean, and optimize your phone number lists. Print-ready. Free to use and share.
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Export your full contact database to CSV with UTF-8 encoding. Ensure special characters and international numbers preserve correctly.
Remove spaces, parentheses, dashes, and periods from phone numbers. Keep only digits and leading plus sign for country codes.
Convert all numbers to international E.164 standard: +[country code][national number], maximum 15 digits. Use the format checker.
Identify and remove exact duplicate numbers. Also check for near-duplicates (same number, different formatting).
Cross-reference every country code against a valid country calling code table. Flag numbers with non-existent codes. See the country format guide.
Validate that each number has the correct digit count for its country. For example: China (11 digits after +86), US/Canada (10 digits after +1), India (10 digits after +91).
Query carrier HLR (Home Location Register) to determine if numbers are currently active on mobile networks. This catches disconnected and deactivated numbers.
Verify which numbers have active WhatsApp accounts. Essential if any part of your outreach involves WhatsApp. Use the WhatsApp checker.
For Telegram-based outreach, verify registration status. Use the Telegram checker. Coverage: 900M+ users.
Check registration across Facebook, Instagram, TikTok, and 40+ other apps simultaneously for comprehensive audience profiling.
Segment numbers into categories: Active / Inactive / Invalid / Unknown. Only Active numbers should go to your marketing lists.
Use the SMS ROI Calculator to quantify savings. A typical campaign with 25% invalid numbers wastes $1,250 per 100K SMS.
Permanently remove numbers classified as Invalid from your marketing lists. These will never convert and harm deliverability.
Export the clean, validated list with a timestamp in the filename. Maintain version history so you can track list quality over time.
Phone numbers go inactive at 20-30% annually. Schedule re-validation every 3-6 months to maintain list quality. Learn why numbers decay.
This checklist was created by 888 Number Check, a phone number verification platform serving marketers and developers across 200+ countries. Each step reflects real-world best practices from processing millions of phone numbers.
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