How to Parse US Addresses in Ruby on Rails

What the API returns

Every response is wrapped in a standard envelope. For parsing, the Result field is a single object whose properties are the address components. This is a real response for 1600 Pennsylvania Ave NW Apt 4B:

{
  "Id": "2737f8f3-af83-4ba1-b9c3-e29d2ba9e03b",
  "Result": {
    "inputAddress": "1600 Pennsylvania Ave NW Apt 4B Washington DC 20500",
    "addressLine1": "1600 PENNSYLVANIA AVE NW",
    "addressLine2": null,
    "addressNumber": "1600",
    "streetPreDir": "",
    "streetName": "PENNSYLVANIA",
    "streetPostType": "AVE",
    "streetPostDir": "NW",
    "unitType": "apt",
    "unitNumber": "4b",
    "city": "WASHINGTON",
    "stateCode": "DC",
    "zipCode": "20500",
    "zip4": null,
    "county": null,
    "matchMode": "Speculative",
    "matchTier": "Near",
    "confidence": 0.7,
    "matchCode": {
      "houseNumber": "Matched",
      "street": "Matched",
      "unit": "Matched",
      "city": "Matched",
      "state": "Matched",
      "zipCode": "Matched",
      "zip4": "NotApplicable"
    },
    "footnotes": ["recovered: standardized via correction, not an exact match"]
  },
  "ClientSessionId": null,
  "StatusCode": 200,
  "IsError": false,
  "Errors": []
}

The fields you'll use most often are covered in the component map below. Note that some fields are empty or null when they don't apply - there's no leading directional here, so streetPreDir is an empty string, and the parser didn't append a zip4 or county, so those are null.

Get your API key

1. Sign up at sthan.io and subscribe to the free Address Parser tier
2. Open your dashboard and create an API key
3. Copy the key - it looks like sthan_live_xxxxxxxxxxxxxxxx

You get the key immediately, with no approval queue. An API key is the simplest way to authenticate: you send it as a Bearer token on every request and there is no separate login step. (If you prefer a short-lived token, there is a JWT flow covered later.)

Configure the project

Keep your key out of source control by reading it from the environment. Net::HTTP and json are both in the standard library, so there's no gem to install:

# Set the key in your shell (or use Rails encrypted credentials)
export STHAN_API_KEY="sthan_live_xxxxxxxxxxxxxxxx"

require "net/http"
require "json"
require "erb"

STHAN_BASE_URL = "https://api.sthan.io"
STHAN_API_KEY  = ENV.fetch("STHAN_API_KEY") # raises early if it isn't set

Build the parser client

Write a small helper that signs each request with your API key, calls the endpoint, unwraps the envelope, and returns the Result hash. Use ERB::Util.url_encode (not CGI.escape) so spaces become %20 - the correct encoding for a path segment:

class ParserError < StandardError; end

def parse_address(address, mode: "speculative")
  encoded = ERB::Util.url_encode(address.strip)
  uri = URI("#{STHAN_BASE_URL}/v2/address-parser/usa/#{encoded}?match=#{mode}")

  request = Net::HTTP::Get.new(uri)
  request["Authorization"] = "Bearer #{STHAN_API_KEY}"

  response = Net::HTTP.start(uri.host, uri.port, use_ssl: true) do |http|
    http.request(request)
  end

  unless response.is_a?(Net::HTTPSuccess)
    response.value # raises Net::HTTPClientException with the status code
  end

  envelope = JSON.parse(response.body)
  raise ParserError, Array(envelope["Errors"]).join(", ") if envelope["IsError"]

  envelope["Result"]
end

That's the whole integration. One call:

result = parse_address("1600 pennsylvania ave nw apt 4b washington dc 20500")

puts result["addressNumber"]   # 1600
puts result["streetName"]      # PENNSYLVANIA
puts result["streetPostType"]  # AVE
puts "#{result['unitType']} #{result['unitNumber']}"           # apt 4b
puts "#{result['city']} #{result['stateCode']} #{result['zipCode']}" # WASHINGTON DC 20500

Choose a match mode

The match parameter controls how much typo tolerance the parser applies while standardizing components. The same call supports four modes, from strictest to loosest:

If you omit match, the endpoint defaults to speculative for the widest recovery. Whichever mode you pick, the location-defining parts of the address - the primary number, ordinal, directional, state, and the street's core name - are never substituted. A looser mode only widens tolerance for misspellings of the same street.

Map the components to your fields

Each component comes back as its own field, so mapping them to database columns is a direct copy. The fields you'll use most:

A few more components cover edge cases: streetPreType, streetPreMod, streetPreSep, and streetPostMod capture pre/post modifiers in unusual street names (for example "Avenue of the Americas"). They're empty for ordinary addresses. Pair the parse with matchCode - a per-component breakdown (Matched / Corrected / Inferred / Unmatched / NotApplicable) - so you can tell which fields were trusted as-is versus corrected. Here is a parse mapped straight to ActiveRecord attributes:

result = parse_address(raw_address)

attributes = {
  address_number:  result["addressNumber"],
  street_pre_dir:  result["streetPreDir"],
  street_name:     result["streetName"],
  street_type:     result["streetPostType"],
  street_post_dir: result["streetPostDir"],
  unit_type:       result["unitType"],
  unit_number:     result["unitNumber"],
  city:            result["city"],
  state:           result["stateCode"],
  zip_code:        result["zipCode"],
  zip4:            result["zip4"]
}

# attributes is ready for ActiveRecord — e.g. Address.create!(attributes)

Wired into a controller, the parse happens server-side and the structured fields go back as JSON. Note this action uses only local variables, so your API key never reaches the browser:

# app/controllers/addresses_controller.rb
class AddressesController < ApplicationController
  # POST /addresses/parse
  def parse
    raw = params.require(:address)
    result = parse_address(raw)

    render json: {
      address_number: result["addressNumber"],
      street_name:    result["streetName"],
      unit_type:      result["unitType"],
      unit_number:    result["unitNumber"],
      city:           result["city"],
      state:          result["stateCode"],
      zip_code:       result["zipCode"]
    }
  rescue ParserError => e
    render json: { error: e.message }, status: :unprocessable_entity
  end
end

# config/routes.rb
post "addresses/parse", to: "addresses#parse"

Alternative: JWT authentication

An API key is the simplest option and is all most apps need. If your security policy prefers short-lived credentials, the platform also supports a 2-step JWT flow. You call GET /Auth/Token once with your profileName and profilePassword headers, receive a token valid for up to 60 minutes, then send that token as the Bearer value on subsequent calls:

def fetch_token
  uri = URI("#{STHAN_BASE_URL}/Auth/Token")
  request = Net::HTTP::Get.new(uri)
  request["profileName"]     = ENV.fetch("STHAN_PROFILE_NAME")
  request["profilePassword"] = ENV.fetch("STHAN_PROFILE_PASSWORD")

  response = Net::HTTP.start(uri.host, uri.port, use_ssl: true) do |http|
    http.request(request)
  end

  JSON.parse(response.body)["Result"]["access_token"]
end

# Then send the token as the Bearer value instead of the static key:
# request["Authorization"] = "Bearer #{fetch_token}"

Everything else - the endpoint, the envelope, the parsing - stays exactly the same. Cache the token and refresh it shortly before the 60-minute expiry rather than fetching one per request.

Handle errors

Two status codes are worth handling explicitly so a hiccup never stalls a batch job:

• 401 - The key or token was rejected. Check the value and, on the JWT flow, refresh and retry once.
• 429 - Rate limit reached. Back off and retry rather than dropping the row.

def parse_with_retry(address, mode: "speculative", retries: 2)
  attempt = 0
  begin
    parse_address(address, mode: mode)
  rescue Net::HTTPClientException => e
    # 429 = rate limited: back off and retry. 401 = bad key: don't retry.
    if e.response.code == "429" && attempt < retries
      sleep(2**attempt) # 1s, then 2s
      attempt += 1
      retry
    end
    raise
  end
end

The exponential back-off (1s, then 2s) is enough for transient limits. For a large backfill, add a small delay between rows and a circuit breaker so one bad minute doesn't stall the whole queue.

What's next: confirm the parsed address is deliverable

Parsing gives you clean, structured components fast. It does not, on its own, confirm that mail or a package will actually arrive - a well-formed address can still point at a unit that no longer accepts delivery. When deliverability matters, run the address through the Address Verification API, which returns a deliverability status and appends ZIP+4 and county. It's the same envelope and the same Net::HTTP pattern - one GET against /v2/address-verification/usa/{address}. The Ruby walkthrough is here: Verify US Addresses in Ruby on Rails.

If you want users to enter a clean address in the first place, Address Autocomplete suggests complete addresses as they type. Prefer Python? See Parse US Addresses in Python.