Blockchain Data APIs: A Complete Guide
Blockchain networks generate enormous amounts of raw, onchain data — every transaction, smart contract interaction, and balance update is recorded on the public ledger. But accessing this data in an understandable way is not as simple as just scrolling through a spreadsheet until you find what you need.
All blockchains run on a network of nodes, and all transaction data is stored within these nodes. However, these nodes were not designed for complex queries, data aggregations, historical analysis or joining transactions across datasets. Directly querying blockchain nodes for their data simply isn’t practical for complex analytics at scale.
This is where blockchain data APIs come in. These APIs are necessary to abstract raw blockchain data into structured, queryable formats that developers, analysts and engineers can actually work with.
In our blockchain API tutorial, we will cover —
- What blockchain data APIs are and how they work
- Why blockchain data is difficult to work with at scale
- What types of onchain blockchain data APIs provide
- Common use cases for blockchain data APIs
- Different approaches to accessing blockchain data
- What to look for in a blockchain data API provider
What Is a Blockchain Data API?
A blockchain data API is a service that provides programmatic access to onchain data, without requiring users to run their own blockchain nodes or build any type of custom indexing infrastructure.
Instead of interacting with raw blockchain data structures — which weren’t built for complex queries in the first place — users can query transactions, blocks, token balances, smart contract events and wallet activity through the API.
You can think of blockchain data APIs as a translation layer between decentralized networks and traditional data workflows. Blockchains are complex, and require specific structures to make their data understandable. Blockchain data APIs handle tasks like data ingestion, indexing, normalization and decoding behind the scenes.
If you work in crypto or blockchain and need access to blockchain data to build your product, it’s essential to use a blockchain data API.
Why Blockchain Data Is Hard to Work With
Although blockchains are famously transparent, public ledgers, they are not inherently analytics-friendly. The sheer amount of raw data stored in blockchain nodes makes it impractical to directly query the nodes themselves when looking for information.
Blockchain data is stored in low-level formats that are optimized for consensus, not analysis. In order to be useful, transaction traces, logs and calldata require decoding by a blockchain data API.
Each blockchain has its own data structures that store data in specific ways. Querying Ethereum data looks very different from querying Solana, Bitcoin or Hyperliquid data. Blockchain data API providers like Allium, which delivers data across over 130 chains, are able to distill data from any supported chain into a usable format.
Without a blockchain data API, it would also be computationally expensive for users to query historical data across the millions of blocks in public blockchain. That massive amount of data requires pre-indexing by an API.
And data can even change as blocks are reorganized, which requires careful handling to ensure the accuracy of the data. Blockchain data APIs exist specifically to solve all of the above problems by standardizing and indexing onchain data — it's why specialized blockchain APIs like Allium were built.
What Data Can You Access Through Blockchain Data APIs?
Most blockchain data APIs have access to a broad set of onchain data types. While exact datasets vary by provider and chain, most APIs consist of several core data categories.
Transaction and Block Data
Transaction and block data is one of the most common types of data queried by blockchain APIs. This data consists of block numbers and timestamps, transaction hashes and statuses, gas usage and fees, and sender and receiver addresses.
Access to structured transaction and block data allows teams to analyze blockchain network activity over time, measure throughput and understand how value moves across the blockchain.
Token and Balance Data
Blockchain data APIs expose detailed token-level data, often normalized across standards such as ERC-20 on Ethereum, or SPL tokens on Solana. These types of datasets may include the following:
- Token transfer events
- Wallet token balances
- Balance changes over time
- Mint and burn events
- Token metadata, such as symbols and decimals
Platforms like Allium provide access to token and balance data commonly used for portfolio tracking, DeFi analytics, and user behavior analysis.
Smart Contract Events
Smart contracts emit events and logs that describe what happens during their execution. However, these events are stored in raw, encoded formats onchain. Once blockchain data APIs decode this information, users will have access to:
- Human-readable contract events
- Function call metadata
- Protocol-specific activity
- Contract addresses and interacting wallets
Blockchain data APIs make it possible to analyze application-level behavior beyond just low-level transactions.
NFT Data
Blockchains that support non-fungible tokens also store data about these specialized NFT datasets. A blockchain data API will be able to provide data about:
- NFT minting events
- Transfers and sales
- Ownership history
- Collection-level activity
- References to off-chain metadata
This type of blockchain data powers NFT analytics, marketplace insights and the tracking of digital asset ownership over time.
Wallet and Address-Level Analytics
Beyond working at the transaction level, blockchain data APIs enable wallet-centric analysis.
Examples include:
- Transaction histories by wallet
- Token holdings per address
- Inbound and outbound transfer analysis
- Address activity over time
Users that are looking for compliance, fraud detection, market research and user segmentation will often use blockchain APIs for wallet-level analytics.
DeFi and Protocol-Specific Data
For popular DeFi applications, many blockchain data APIs also expose protocol-aware datasets. This can include:
- Liquidity pool activity
- Swaps, deposits and withdrawals
- Lending and borrowing events
- Protocol revenue and fees
By abstracting protocol-level data into structured tables, blockchain data APIs make it easier for users to analyze DeFi activity without needing to write custom parsers for each protocol.
Historical vs Real-Time Data
Blockchain data APIs typically support both historical and near real-time access. However, how real-time the access is will vary by provider.
Access to historical data makes long-term trend analysis and research possible, while real-time data supports monitoring, alerts, live dashboards and products.
For analytics-focused workflows, deep historical coverage provided by blockchain APIs is often more important than the raw speed of real-time access. Platforms like Allium focus on providing historical, analytics-ready blockchain data that can be queried at scale, making them particularly useful for data teams and researchers.
Common Use Cases for Blockchain Data APIs
Blockchain data APIs are commonly used for analytics, monitoring, compliance, and research. Teams can use blockchain APIs to build real-time dashboards to monitor transactions, track digital asset ownership over time, analyze user wallet behavior and more.
Both web3 startups and large financial institutions often use blockchain data APIs to power their products — as an example, Visa uses Allium’s blockchain data API to power their onchain analytics dashboard for fiat-backed stablecoins.
Analytics and Dashboards
Data teams power internal dashboards with blockchain APIs, tracking protocol usage, revenue and user activity over time.
By using indexed and normalized blockchain data, teams can:
- Monitor daily and monthly active users
- Measure transaction throughput and fees
- Track protocol revenue and growth trends
- Build internal or public-facing dashboards
DeFi Protocol Monitoring
Decentralized finance protocols heavily depend on onchain data to understand how their own systems are being used.
DeFi protocols can use an API to monitor:
- Liquidity levels and total value locked (TVL)
- Deposits, withdrawals, and swaps
- User behavior across smart contracts
- Protocol performance and risk exposure
DeFi teams need to respond quickly to changes in usage or market conditions, which is why they need blockchain APIs to give them consistent access to smart contract events and token flows.
Compliance and AML
Compliance teams at financial institutions and exchanges use blockchain data APIs to analyze wallet activity and transaction flows at scale.
Common applications include:
- Monitoring large or unusual transactions
- Tracing funds across addresses
- Identifying exposure to sanctioned or high-risk wallets
- Supporting anti-money laundering (AML) workflows
These types of use cases require intensive, accurate historical data and the ability to query data across long time ranges — capabilities that raw node access do not easily provide.
Portfolio and Wallet Tracking
Both consumer and institutional applications rely on blockchain data APIs to support tracking of their users’ portfolios and wallets. These APIs make it possible to:
- Track token balances over time
- Monitor inbound and outbound transfers
- Calculate portfolio performance
- Support multi-chain wallet views
Unified data access is especially important for applications that span multiple blockchains.
Data Research and Reporting
Analysts, researchers and media organisations often use blockchain data APIs to study blockchain networks and market behavior.
With access to historical onchain data, researchers can:
- Analyze long-term network trends
- Study user adoption patterns
- Measure protocol growth and decline
- Produce data-driven reports and insights.
Types of Blockchain Data APIs
Not all blockchain data APIs are built the same.
Depending on what a user is looking for with their blockchain analysis, there are several different types of APIs that can offer specifically what is needed, whether that be real-time queries, chain-specific queries, or deep historical analysis. Blockchain data APIs generally fall into several categories based on how data is indexed and accessed, below is a list of examples.
Node-Based (RPC) Blockchain APIs
Node-based APIs expose blockchain data directly from full or archive nodes using interfaces like JSON-RPC. These types of APIs are the most low-level way to access blockchain data, since they directly mirror how blockchains operate internally.
This type of API is well-suited for:
- Broadcasting transactions
- Fetching individual blocks and transactions
- Reading current onchain state
However, node-based APIs are poorly suited for analytics due to their limited querying capabilities. They allow only minimal indexing, and don’t support deep historical analysis. As a result, node-based APIs are usually used for application logic, and not data analysis.
Indexed Blockchain REST APIs
Indexed REST APIs sit on top of blockchain nodes and provide pre-processed endpoints for common queries. Rather than fetching raw blocks or logs, users can request higher-level data like token transfers, wallet activity or contract events through HTTP endpoints.
These APIs are easier to use than raw node access, and are commonly used for:
- Application backends
- Wallet and explorer features
- Basic analytics use cases
The trade-off with using this type of API is flexibility — indexed REST APIs usually expose a fixed set of endpoints and query parameters, making it difficult to run custom or exploratory analysis beyond what the API was designed to support.
SQL-Based Blockchain APIs
SQL-based APIs expose onchain data in relational tables that can be queried using standard SQL. These types of APIs are particularly well-suited for analytics, reporting and data science workflows.
With SQL-based APIs, users can:
- Run complex historical queries
- Aggregate and group data over time
- Join blockchain data with off-chain datasets
- Use familiar BI and analytics tools
Blockchain data platforms like Allium focus on the SQL-based blockchain API model, providing unified, analytics-ready blockchain data that integrates with modern data warehouses. For data teams already working in SQL, this significantly lowers the barrier to entry for using blockchain analytics, a sign of customer success.
Streaming and Event-Based Blockchain APIs
Streaming and event-based APIs focus on delivering near real-time blockchain data. Rather than supporting ad hoc queries, these APIs push data as events occur onchain.
They are commonly used for:
- Real-time monitoring and alerts
- Trading and liquidation systems
- Automation and bot infrastructure
While streaming APIs are valuable for time-sensitive applications, they are typically not designed for deep historical analysis or exploratory queries.
Which Blockchain Data APIs Support Fast Data Retrieval?
If a team is looking for fast data retrieval and real-time data, then streaming and event-based blockchain APIs, as well as RPC blockchain APIs, are best-suited for that use case. Node-based RPC APIs and streaming APIs are fastest for new blocks and transactions, event-driven systems, and bots, liquidations and alerts.
However, while these types of APIs are fast for single events, they are not practical for deeper analytics, aggregation or historical queries. If a team’s use case is to quickly query large volumes of historical data, then platforms like Allium using SQL-based blockchain data APIs are often fastest for large historical analytics because they pre-index blockchain data and support query engines designed for large scale scans and joins.
In summary: node-based and streaming APIs are fastest for real-time events, while SQL-based blockchain data APIs are fastest for querying large volumes of historical data.
How SQL-Based Blockchain Data APIs Work
SQL-based blockchain data APIs turn raw blockchain data into structured, relational tables. This approach allows teams to analyze blockchain activity without building custom indexing systems or learning low-level blockchain interfaces.
Platforms like Allium expose blockchain data through SQL by indexing and normalizing onchain activity into unified schemas. This makes it possible to run cross-chain queries, compare activity across networks and join blockchain data with offchain datasets.
SQL-based blockchain data APIs often integrate directly with data warehouses such as Snowflake or BigQuery, enabling teams to incorporate blockchain data into existing analytics pipelines. With support for consistent schemas, data freshness, and analyst-friendly workflows, this model is particularly well suited for teams focused on reporting, research, and data-driven decision-making rather than infrastructure management.
What to Look for in a Blockchain Data API Provider
Choosing a blockchain data API provider comes down to what capabilities are required — a need for deep historical analysis, real-time data or specific chain coverage will dictate which API will work best.
Chain coverage is an essential consideration when choosing a blockchain data API. As blockchain activity becomes increasingly multi-chain, broad and consistent coverage across blockchains is essential. A blockchain data API should support the networks that a user or a team needs to cover, like Ethereum, Solana, Hyperliquid, Bitcoin and others.
Historical depth is another important factor when picking an API — many use cases require years of historical blockchain data, not just recent activity and real-time data. API providers that offer deep, well-maintained historical datasets give teams more reliable insights for long-term trend analysis.
Data freshness and latency matter when a user needs near real-time monitoring. Users need to understand how quickly new blocks and transactions are reflected in the API, and whether this aligns with their operational needs.
Schema consistency and data quality are especially important for teams working across more than one blockchain. Consistent schemas make cross-chain analysis easier and less error-prone, since there is no need for chain-specific logic.
Query flexibility will determine how much control users have over their data. An API that supports complex filters, aggregations and joins are better suited for exploratory analysis that has evolving analysis.
Documentation quality, reliability and uptime also need to be considered when choosing a blockchain. Clear documentation will reduce a user’s onboarding time, and dependable infrastructure means that downstream systems and analyses will remain stable.
Making sure that an API is able to integrate with a user’s existing data tools will make it more usable — providers that integrate with data warehouses, BI tools and analytics platforms means that a user won’t need to build a new, isolated analytics system.
Allium differentiates itself from other blockchain data API providers with its emphasis on unified schemas and SQL-first access. Data teams and analysts looking to work with blockchain data using familiar tools and methodologies are likely to find success using Allium.
Blockchain Data APIs vs Running Your Own Infrastructure
Some teams might consider building their own blockchain data pipelines rather than relying on third-party blockchain data APIs. While this means that teams are in full control of the API, there are significant tradeoffs that make building in-house less attractive.
Running your own infrastructure requires managing full or archive nodes, building and maintaining custom indexers, handling chain reorganizations and data quality issues, and continuously scaling storage and compute as values grow. This type of heavy infrastructure is resource-intensive and may divert attention away from analysis and product development.
On the other hand, using an already existing blockchain data API shifts the operational burden to a specialized provider. Blockchain data APIs offer lower ongoing maintenance costs and access to consistently indexed, analytics-ready data. Platforms like Allium are a clear example of the benefits — Allium provides structured, SQL-accessible blockchain data designed for analytical workflows.
Blockchain APIs are generally the more efficient and sustainable path for a team, unless operating blockchain data infrastructure itself is a core part of the business.
Frequently Asked Questions About Blockchain Data APIs
As teams evaluate how to work with onchain data, several common questions tend to come up
What Is the Difference Between a Blockchain Data API and a Blockchain Node?
A blockchain node stores and validates raw blockchain data, but it is not designed for analytics or complex queries. A blockchain data API sits on top of nodes — it indexes and normalizes onchain data so it can be queried efficiently for analytics, reporting and application development.
Do I Need to Run My Own Nodes to Use a Blockchain Data API?
No. Blockchain data APIs provide access to onchain data without requiring users to run full or archive nodes or maintain custom indexing infrastructure. This significantly reduces operational overhead and complexity.
Are Blockchain Data APIs Real-Time?
Some blockchain data APIs support near real-time data access, particularly streaming and event-based APIs. Analytics-focused blockchain data APIs prioritize data accuracy and historical depth, often trading milliseconds of latency for reliability and query performance at scale.
Can Blockchain Data APIs Be Used for Analytics and Reporting?
Yes. Many blockchain data APIs — especially SQL-based platforms like Allium — are built specifically for analytics and reporting. They allow users to run complex historical queries, aggregate data, and integrate blockchain data into BI tools and data warehouses.
Do Blockchain Data APIs Support Multiple Blockchains?
Most modern blockchain data APIs support multiple chains, though coverage varies by provider. Multi-chain platforms like Allium unify data across many blockchains into consistent schemas, making cross-chain analysis significantly easier.
The Future of Blockchain Data APIs
Blockchain data APIs are foundational to the infrastructure of the Web3 industry. As we see a deeper integration with AI and LLM-driven analysis, an increased demand from traditional data teams exploring the new Web3 space and growing cross-chain abstraction, it’s clear that the need for blockchain data APIs will only grow.
Blockchain APIs play a critical role in making onchain data accessible, usable and scalable. Platforms that prioritize quality and interoperability, like Allium, will allow blockchain data APIs to become the backbone of modern blockchain analytics.
