Beyond Regex: Why Syntactic Validation Isn't Enough for Viber Outreach

When building outreach systems, it is tempting to rely on regex or length checks to validate contact lists. However, relying solely on syntactic validation often leads to "ghost" lists—where your database appears clean, but your messages fail to reach active users. In reality, platform-specific registration status is the only reliable indicator of reachability.

The Problem with Syntactic Validation

Many developers assume that if a phone number follows the E.164 format, it is a valid target for messaging. This is a dangerous assumption. A number might be syntactically correct but disconnected from the target platform, or simply inactive. Relying on basic format checks means you might spend resources targeting dead ends that appear to be valid.

Moving to Platform-Aware Verification

To ensure your outreach is effective, you need to verify if a number has an account registered on the specific platform you are targeting, such as Viber. This requires an asynchronous batch workflow that checks your list against the platform's actual registration status.

Step 1: Prepare Your Data

Normalization is the first step. Ensure your phone numbers are in E.164 format. Your input should be a simple text file with one number per line:

[phone]
[phone]

Step 2: Submit Your Batch

Using the viber task type, you can submit your file to the https://api.numberchecker.ai/v1/tasks endpoint. This returns a task_id that you will use to track the progress of your verification.

curl --location 'https://api.numberchecker.ai/v1/tasks' \
--header 'X-API-Key: YOUR_API_KEY' \
--form 'file=@"./input.txt"' \
--form 'task_type="viber"'

Step 3: Poll for Completion

Because this is an asynchronous process, you must poll the https://api.numberchecker.ai/v1/gettasks endpoint using your task_id. Do not treat pending or processing statuses as final. Wait until the status reaches exported.

Step 4: Process Results

Once the status is exported, the result_url will provide a download link to your processed data. Each row in the result file will contain the original number and an activated flag (e.g., "yes"). This activated field is the source of truth for your outreach strategy.

Best Practices for Integration

• Handle Asynchronicity: Always implement a polling loop that checks the status field.
• Respect Limits: Check the current documentation for input limits before uploading large batches.
• Downstream Mapping: When processing the result file, preserve the returned column names to ensure your internal database updates remain consistent.

Conclusion

Syntactic validation is only the beginning. By integrating platform-aware verification into your pipeline, you can filter out inactive contacts before they impact your outreach metrics. For more details on implementing these checks, refer to the official documentation.

This article was drafted with AI assistance and reviewed before publishing.