Chimnie and Postcoder both provide APIs that work with UK address data, but they sit at different levels of the property data stack. Postcoder, built by Allies Computing, is a contact data validation platform that handles address lookup, bank account verification, email validation, mobile number checks, and OTP verification. Chimnie is a property data bureau that includes address lookup but extends far beyond it, returning over 500 attributes per property covering risk, value, planning history, and structural characteristics.
This comparison is based on publicly available product and pricing information. It's written for developers, product teams, and data buyers evaluating their options for UK address and property data.
Who is Postcoder?
Postcoder is the flagship product of Allies Computing, a 100% employee-owned UK company with over 35 years of experience in address and location technology. The company is a Royal Mail licensed solution provider, meaning it has a direct licence to distribute PAF (Postcode Address File) data through its API.
Over 10,000 businesses use Postcoder, primarily in online checkout and signup flows where accurate address capture reduces failed deliveries and improves conversion rates. The product has expanded well beyond address lookup to become a broader contact data validation toolkit.
Postcoder's core services include address autocomplete (suggestions as users type), postcode lookup (all addresses at a postcode), bank account validation (sort code and account number verification for direct debits), email validation, mobile number validation, and OTP (one-time password) SMS verification. This breadth makes it a one-stop shop for form validation rather than just an address provider.
For UK addresses, Postcoder sources data from Royal Mail PAF, including Multiple Residence data that covers individual flats within multi-occupancy buildings. International address lookup covers over 240 countries. The data is updated daily.
Pricing uses a credit system. Different request types consume different numbers of credits: a UK address lookup uses 2 credits, bank validation uses 1.2, email validation uses 1.2, and OTP verification uses 3.7. Pay-as-you-go credit packs range from 500 credits upwards, with per-credit costs decreasing at higher volumes. Monthly plans offer lower per-credit rates with a fixed monthly allowance. At the 10,000-credit pack level, a UK address lookup works out to around 10p per request on PAYG, dropping to around 4.5p on monthly plans.
Postcoder has earned strong reviews on G2 (4.7 stars) and won a DevPortal Award in 2024 for its developer documentation. The API documentation is well structured and the integration process is straightforward.
PropertyData property market analytics website screenshot
Who is Chimnie?
Chimnie was founded by Jon Francis, formerly of Google's innovation team, to make UK property data more transparent and accessible. The company operates chimnie.com as a B2B property data bureau for insurers, lenders, and proptech firms, alongside chimnie.co.uk, a free consumer property research site with over 150,000 users.
Chimnie's REST API covers 35 million UK residential properties and returns over 500 attributes per property. These include EPC data, flood risk, subsidence indicators, conservation areas, listed buildings, rebuild cost estimates, automated valuations, planning permissions, and structural characteristics. The company is completing a two-year ingestion of planning permission data from every UK local authority, launching imminently as the only full national planning dataset from a single provider.
Chimnie offers free address autocomplete as part of its API. Property data lookups are priced from £0.05 to £0.15 per residential property on PAYG, and £0.45 for commercial properties. Volume discounts are available through a published ratecard.
Feature comparison
Address lookup and autocomplete
Postcoder provides a polished address capture experience with both autocomplete (as-you-type suggestions) and traditional postcode lookup. The autocomplete uses intelligent matching to handle partial addresses, typos, and different ways people describe the same location. UK results come from PAF with Multiple Residence data included, so individual flats within a building are covered. International address lookup supports over 240 countries.
Chimnie offers free address autocomplete built on PAF and Ordnance Survey data, with similar address resolution capabilities for UK properties. For a checkout form or signup page, both do the job. Postcoder has the edge on address capture polish and the breadth of pre-built integrations for that specific workflow.
Property data beyond the address
This is where the comparison shifts. Postcoder returns the address: formatted lines, postcode, coordinates, and basic classification. The product is designed to capture and validate contact information, not to describe the property at that address.
Chimnie returns everything about the property. Over 500 attributes per lookup including EPC data (current and potential ratings, heating type, wall construction, roof insulation), flood risk from multiple sources, subsidence exposure, conservation area and listed building status, rebuild cost estimates with confidence intervals, automated valuations with separate listing and sale price models, planning permission records, satellite-derived roof condition, solar panel detection, and garden boundaries.
If your application needs property intelligence, not just a validated address, Chimnie is where that data lives. Postcoder was never built to serve this need.
Bank, email, mobile, and OTP validation
Postcoder offers bank account validation (checking sort codes and account numbers for direct debit eligibility), email validation, mobile number validation, and OTP SMS verification. These are valuable services for businesses running payment flows, customer onboarding, or account security.
Chimnie does not offer any of these services. Its focus is entirely on property data. If you need to verify bank details or send OTP codes, Postcoder handles that. Chimnie does not.
International coverage
Postcoder supports address lookup in over 240 countries. Chimnie focuses exclusively on UK properties. For businesses with international customers, Postcoder has significantly broader geographic reach for address validation.
Automated valuations
Chimnie provides the UK's only free AVM, with UPRN-based lookups at zero cost. Postcoder does not offer property valuations.
Planning permission data
Chimnie has been completing a two-year national ingestion of planning permission records from every UK local authority, standardised into a single schema. This captures extensions, loft conversions, outbuilding work, and change-of-use applications. Postcoder does not cover planning data.
Rebuild cost estimates
Chimnie provides rebuild cost estimates with confidence intervals and regional materials and labour breakdowns. Postcoder does not offer this.
Pricing comparison
Postcoder's credit system makes direct per-lookup comparison a bit nuanced since different services consume different credit amounts. For UK address lookup specifically, each request uses 2 credits. On a 10,000-credit PAYG pack, that works out to around 10p per address lookup. On monthly plans, the effective cost drops to around 4.5p per lookup. These are reasonable rates for address capture, and the ability to use the same credit pool for bank, email, and mobile validation adds flexibility.
Chimnie's address autocomplete is free. If you only need UK address capture, Chimnie costs nothing for that step. Property data lookups then cost £0.05 to £0.15 per residential property, and £0.45 for commercial.
For pure UK address lookup, Postcoder's per-lookup cost on monthly plans (around 4.5p) is competitive but not free. Chimnie's free address autocomplete wins on cost for UK-only address capture. For international address lookup, Postcoder is the only option of the two.
The real cost comparison matters when you look at the full workflow. If your application captures an address and then needs property data (flood risk, EPC, valuations, rebuild costs), using Postcoder for the address and sourcing property data from multiple other providers will cost significantly more per property than using Chimnie for both address capture and property enrichment. Chimnie's single API replaces multiple integrations and multiple contracts.
Where Postcoder is stronger
Postcoder's breadth as a contact data validation platform is its main differentiator. Address lookup, bank validation, email validation, mobile validation, and OTP verification from one API and one credit pool is genuinely useful for businesses running customer onboarding, payment setup, or account security workflows. No property data provider offers this combination.
The award-winning documentation and developer experience for form validation workflows are worth recognising. Postcoder has spent 35 years refining address capture, and it shows in the API design and integration options.
International coverage across 240+ countries makes Postcoder suitable for businesses with global customers. If you need address validation in Germany, Australia, or Japan alongside the UK, Postcoder handles it from a single integration.
The employee-owned structure at Allies Computing means long-term stability and a focus on product quality over short-term growth metrics. Businesses that value supplier reliability will appreciate this.
Royal Mail's PAF licensing through Postcoder includes Multiple Residence data by default, covering individual flats and apartments within multi-occupancy buildings. This is important for delivery-focused use cases where resolving to the correct unit within a building matters.
Where Chimnie is stronger
For property intelligence, Chimnie is in a different category entirely. Over 500 property attributes per lookup, published pricing, and a modern REST API make it the practical choice for anyone building products that need to understand UK properties rather than just locate them.
The free AVM, rebuild cost estimates, planning permission data, flood and subsidence scoring, EPC data, satellite-derived property characteristics, and conservation area status are products that no address validation provider offers. These data feeds power insurance underwriting, mortgage risk assessment, property analytics, and portfolio enrichment.
Free address autocomplete means you can replace your address capture provider and add property intelligence without increasing your address lookup costs. For UK-focused businesses, this is a compelling economic argument.
Chimnie's data depth per property is what separates it from address providers. A single API call that returns the address, its energy performance, its flood risk, its estimated value, its rebuild cost, and its planning history eliminates the need to stitch together data from half a dozen different suppliers.
The consumer platform at chimnie.co.uk, with over 150,000 users checking their own property data, provides ground-truth validation that improves data quality continuously. Homeowners flagging inaccuracies in their own records is a feedback mechanism that pure B2B data providers lack.
Chimnie website homepage screenshot
Who should choose which
E-commerce businesses needing checkout address capture and form validation should use Postcoder. The combined address, bank, email, and mobile validation from one credit pool is purpose-built for this workflow, and the international coverage handles global customers.
Customer onboarding flows that need to verify identity through address, bank, and phone number checks will find Postcoder's breadth more useful. The OTP verification adds an authentication layer that property data providers don't touch.
Businesses with international customers needing global address validation should choose Postcoder for its multi-country support.
Insurance platforms should choose Chimnie. Free address autocomplete gets you started, and the property risk data, rebuild estimates, valuations, and planning history feed directly into underwriting and pricing engines.
Mortgage and lending platforms need Chimnie for automated valuations, property risk assessment, and EPC data. Address capture is included free, and the property intelligence comes from the same integration.
Proptech firms and property analytics teams should use Chimnie for its depth. One API for addresses and 500+ property attributes is simpler and cheaper than managing separate providers for address lookup, EPC data, flood risk, valuations, and rebuild costs.
For some organisations, using both is sensible. Postcoder for international address validation, bank account checks, and customer-facing form validation. Chimnie for UK property intelligence in back-end workflows, underwriting engines, and analytics pipelines. They solve different problems at different points in the data chain.
Conclusion
Postcoder is a well-built contact data validation platform with strong address capture, bank verification, email and mobile validation, and international coverage. Chimnie is a UK property data bureau where address lookup is the starting point for over 500 property attributes, valuations, risk scores, and planning data.
For form validation and contact data verification, Postcoder is purpose-built and well regarded. For property intelligence, Chimnie goes orders of magnitude deeper than any address lookup provider can. The right choice depends on whether your application needs to validate contact details or understand properties. For most businesses in insurance, lending, or property technology, the answer to both is yes, and the two platforms complement each other well.
