What is a WebID in PI Web API and how does it work?

Every object in PI Web API (points, elements, attributes, databases) is identified by a WebID — a URL-safe, base64-encoded string.

WebID Format

A WebID encodes:

• The object type (PI Point, AF Element, AF Attribute, etc.)
• The server identity
• The object's unique identifier (tag name hash, element GUID, etc.)

Example: P0HkABVFRIUYJER9RV1MX0RBVEEuWCwMRkxPVy5QVg

How to Get WebIDs

Search Endpoint

GET /piwebapi/points?nameFilter=Sinusoid
→ Returns objects with their WebIDs

Path-Based Lookup

GET /piwebapi/points?path=\\PIServer\Sinusoid
→ Returns the point with its WebID

WebID 2.0 (Generate Client-Side)

PI Web API 2019+ supports WebID 2.0, which you can construct without an API call:

import base64

def encode_webid_point(server_name: str, tag_name: str) -> str:
    marker = "P1DP"  # PI Point type marker
    server_encoded = base64.b64encode(
        server_name.upper().encode('utf-16-le')
    ).decode().rstrip('=')
    tag_encoded = base64.b64encode(
        tag_name.upper().encode('utf-16-le')
    ).decode().rstrip('=')
    return f"{marker}{server_encoded}{tag_encoded}"

Tips

• Cache WebIDs — they don't change unless the object is deleted and recreated.
• Use WebID 2.0 to avoid initial lookup calls when you know the object path.
• WebIDs are case-sensitive.
• Include the WebID in your application's data model for fast subsequent API calls.