Bitcoin Forum

Hello,

I am compiling a list of bitcoin APIs. Note that I am not interested in collecting block explorer web interfaces, but APIs for developers.

"Data" APIs

Requirements:

• some sort  of HTTP API (eg, REST)
• query the blockchain: blocks and transactions
• p2p network: unconfirmed transactions, push transactions
• query addresses: transactions, balances, unspents

(so basically everything one needs for building a web wallet)

Hosted:

• blockchain.info (https://blockchain.info/api/blockchain_api)'s blockchain data API [websockets]
• chain.com (https://chain.com/docs) [webhooks, websockets]
• Blockstrap (http://docs.blockstrap.com/en/api/) (as part of their app platform)
• Blockcypher (http://dev.blockcypher.com/) [webhooks, websockets]
• Toshi (https://toshi.io/docs/) by Coinbase [websockets]
• Blocktrail (https://www.blocktrail.com/api/docs#api_data) [webhooks, multisig]
• blockr (https://btc.blockr.io)  [websockets]
• smartbit (http://smartbit.com.au)  [websockets]

Self-Hosted:

• Insight API (https://insight.is/) (self hosted open-source, by BitPay) (Hosted versions exist, see below (https://bitcointalk.org/index.php?topic=942633.msg10332544#msg10332544)) [websockets]
• Bitcore node (https://github.com/bitpay/bitcore-node/) (self hosted open-source using BitPay's "bitcore" API) (successor of Insight API) [websockets]

Discontinued:

• Hello, Block! (https://helloblock.io/docs/ref) offline as of 1/4/2015

High-level wallet APIs

• blockchain.info (https://blockchain.info/api/blockchain_wallet_api)'s blockchain data API
• Block.io (https://block.io)  [webhooks, multisig]
• BitGo (https://bitgo.com)  [cosign]
• Gem (https://gem.co)  [webhooks, cosign]

Additions/suggestions/corrections?

You might find this post useful...


If you know more, please add in this thread: https://bitcointalk.org/index.php?topic=636463.0

Thanks, that was exactly what I was looking for (but with search disabled...)

Search is now enabled on this forum. :)

Actually, after a second glance, not really. :) The focus of the other thread is block explorers, not the discussions of APIs.
So it seems that most people report their favorite block explorer for occasional manual use,
rather programmatically usable APIs that support a bigger feature set. Most of the sites listed
don't have an API.

Yes it is. blockchain API still leads.

Sorry, I don't understand what you mean. "still leads" = is still the best? Neither is that really related to my statement that the other thread focuses on user-oriented block explorers, nor is it true...

blocktrail has an API and I personally never had any problems with it. I should clarify though that I did not use their API for anything serious.

Nice, thanks, blocktrail is one I didn't know about. I'll update the thread.

Does anyone know "Gem"? https://gem.co/

Just found it, but they are in closed beta, so I have no idea what they actually offer  ???

There also used to be https://plugchain.com/ by CEX.io, but it seems to be offline. Does anyone know what happened to it?

Try to list those especially offering bitcoin send/receive API. AFAIK none still offers it as good as blockchain.info, though it is difficult to offer a send API for those, who do not have a wallet service.

One can self-host insight which is nifty, but also not clear that you know but there are at least 3 instances of insight available:
- https://insight.bitpay.com/ e.g. https://insight.bitpay.com/api/status?q=getBestBlockHash
- https://search.bitaccess.ca/ e.g. https://search.bitaccess.ca/api/status?q=getInfo
- https://chain.localbitcoins.com/ e.g. https://chain.localbitcoins.com/api/block/000000000000000006bade384570a3d3209e7358a93630df4add40911a42f5da

Description of the api: https://github.com/bitpay/insight-api

I am not particularly interested in a high-level wallet API (as I prefer to build transactions myself),
but I can see that it's very interesting for others so I'll add a section for it.

Great, thanks, I'll add a note to my main post. If these instances will stay around is of course questionable - except the Bitpay one, maybe.

localbitcoins is also in use at the site of the same name so I presume that's their reference for checking trades there.  So I'd imagine that would also be fairly stable one.
All three sites have been up since I became aware of insight.

Can I challenge you to try our API and see if you still think bc.info is the best ?
Im from the https://www.blocktrail.com/ (https://www.blocktrail.com/) team, if you need any help I can get our team to help you with the integration.

I dint say bc.info is great in terms of normal blockchain API. I said it in terms of 2 specific functions required by merchants... the send & receive API. bc.info is becoming monopoly in providing these 2 specific service, which I think is bad.

Sorry for my miss understanding there,
We do offer send and receive but only for BTC not a conversion to dollars or euro, is this where you are looking for ?

To be specific, I'm looking for alternative to the following 2...

i. https://blockchain.info/api/api_send

ii. https://blockchain.info/api/api_receive

If you are offering similar alternative, can you please point me to the specific links on https://www.blocktrail.com/api/docs ? Conversion to any FIAT is not the requirement. bc.i does not offer it either.

The main issue with blockchain.info (and many other APIs) is that they have direct access to your coins. It's originally a webwallet where your password never leaves your browser, but their API requires you to provide their server with the password and thus gives them custody of your coins.
You'll never need to do that with BlockTrail because the transactions are created and signed on the client side using the SDK, and are then co-signed and broadcasted via BlockTrail.

The blockchain.info receive API actually makes the bitcoins go to their own address first before the coins come to you, again, giving them full custody of your coins.
This is done for various technical reasons and are considered bad practice nowadays - the main reason being that you can't monitor your own addresses for transactions and that they have a max amount of addresses (which is because you need to backup every private key for each address).

The Blocktrail Wallet API is a HD Wallet, so you can have unlimited addresses, create a new one every time you need to receive coins (as best practices dictate) and because of the HD 'magic' you never even need to create new backups.
And we also have 'webhooks' which allow you to get notifications ( we send data to your server using a HTTP POST ) when your addresses receive transactions.

Initialize SDK

Create a wallet

Setup transaction notifications

Receive a transaction
you'll be automatically subscribed to notifications on these new addresses

Send a transaction

Get wallet balance

If you need any help feel free to email us or join us on #blocktrail on irc.freenode.net !

I added tags that indicate whether an API supports websockets, webhooks, or some additional multi-signature functions. I didn't have the time to wade through it all in detail, so things might not be correct. If you spot an error, let me know!

I am working on a site which I hope to announce before block 34400, www.querytheblockcha.in (Home page will throw an error).  PM me if you want a sneak peak.

What will be the purpose? An overview as given here or a data api in itself? Also, before block 34400 might be hard... ;)

Great list, thanks! I just tried out Insight and I'm pretty happy so far.

What is the difference between websockets & webhooks ?

It's great to have an API that one can self-deploy, but unfortunately it's pretty darn slow. I experimented with Toshi recently, which seams considerably faster - but I haven't had the time yet to deploy it myself, so I can't compare properly.

Imagine you want to get all incoming transactions for your address.
With webhooks, you have an API endpoint on your service. You give
that endpoint to the service provider, and everytime they see a new
transaction to your address they post it to the endpoint you've
provided.

With websockets, you establish a continuous connection to the service
using WebSockets (http://en.wikipedia.org/wiki/WebSocket), thereby subscribing to updates regarding
transactions for your address. As long as you keep the connection open,
the service will publish new transactions to your address on this websocket
connection.

Both have advantages and disadvantages. Webhooks are plain http and thus
have no technological overhead. However, you need a stable endpoint
(a server). WebSockets is an additional protocol, and thus you might face
problems (extra libraries and infrastructure needed). However, you can
initiate them from anywhere, also from mobile devices for example.

Does your project and API support or implements green addresses? I am looking for a green address implementation/API other than the https://greenaddress.it one.

What's a "green" address?

No, BlockTrail uses 2-of-3 multisig (unlike greenaddress which makes use of 2-of-2), so BlockTrail does not have the control over the coins to prevent its users from double spending (and thus does not provide "greenaddress functionality" between its users)

This is probably the best explanation for that question at https://en.bitcoin.it/wiki/Green_address

Generally I understand what multisig is for but could you explain in the case of BlockTrail service why need their signature for the transaction, what's the advantage of having a multisig transaction and BlockTrail's signature on the transaction?

Great quesiton. I'll give an example to help illustrate the problem and how 2-of-3 multisig solves it.

Lets say you run a bitcoin service of some sort, for example, an exchange, a gambling website, an ATM network, etc. One morning you wake up to find that $1,000,000 worth of bitcoins are missing from your hot wallet :o

If you were using 2-of-3 multisig, this scenario could have been prevented, because the service provider (for example BlockTrail (https://www.blocktrail.com)) could enforce your custom restrictions and spending limits before signing your transactions. This allows you to greatly mitigate how much damage an attacker can do (i.e you would lose $10k instead of $1m). In order to circumvent the restrictions, an attacker would need to have access both to your systems AND the multisig service provider's systems, making it very unlikely for a successful attack.

In another scenario, if the multisig service provider's systems are breached, then users' coins are still safe, because the service provider only has 1 out of 3 keys needed to make transactions. An attacker would still need to attack every single user individually, to actually get their bitcoins. This isn't necessarily the case with some of the more traditional APIs which either have access to your private key (coinbase) or which you need to send your password to the service provider (bc.info).
   
Since we're on the topic of security I think its worthwhile mentioning some of the benefits of HD Wallets, which separate your keychain from your backup process. The issue is that if your bitcoin service (exchange, gambling site, ATM, etc) is constantly generating new bitcoin addresses for users to pay and deposit into, in a short while you'll find that you need to manage hundreds, or hundreds of thousands of private keys. If you have a high volume of transactions its likely that you have a very well defined backup process for getting these keys into cold storage.

HD wallet technology eliminates this issue entirely - since you have one private key to manage all of your bitcoin addresses, forever, and you only need to back it up once when you initially created it. You can generate it, throw it in a safety deposit box and never need to expose your backup process to technical faults, human errors or unknown security vulnerabilities. This is also far easier to manage and gives you peace of mind.

Thanks for answering, that's great, the multisig makes a perfect sense from security viewpoint. On the other hand what happens terms of transferring the coins if the service provider, in this case BlockTrail goes out of business? Since the service provider won't be able to sign the transaction how the coins can be transferred from my address? The BlockTrail website states that "You're always able to spend your coins using your primary key together with your backup key", is that means 2 keys from the three (which are my key, backup key and BlockTrail's key) are enough to perform a transaction?

I am actually planning to accept Bitcoin within our business and searching for an online wallet solution that offers a robust API as well. The Blockchain.info service is a great and matured solution, but I am concerned that Blockchain.info keeps full control over the wallet, while BlockTrail claims that they address this issue by letting users retain full control over the wallet. The BlockTrail API looks good as well, it seems the team at BlockTrail has done a great job so far.

Terms of the HD wallet, again, to mitigate the risk of the service provider BlockTrail goes out of business, should users make a backup of their wallet after every transaction or how can be the coins accessible in case if the BlockTrail servers aren't operational?

Hey Tzpardi,

Again excellent question. Even if a meteor falls down directly on BlockTrail HQ and we are no longer able to sign a transaction, you STILL have access to your coins because you have 2 out of 3 keys, and two keys are always necessary to sign your transactions. So if BlockTrail is not around, you take the second key that you kept in cold storage and you sign your coins using your own two keys. You can do this manually, but we'll also be adding a tool to our SDK to help you do this easily.

The beauty of HD wallet capabilities is that you never need to backup anything except for the 'master seed'. This is because using cryptography, you can recover all your addresses (and their keys) from this master seed. So essentially, after you've secured your master seed in a safe, you never need to make a backup ever again!

Is this thread about apis or multi-sig?

Is there any API offered by blocktrail.com that allows to Push a Tx, e.g. https://blockchain.info/pushtx ?

not in this format, no.

You may say if it is available in any other format...

Others do offer this service: Hello Block, chain.com, toshi...
 (Note that the "push" functionality might have different names such as "propagate", "publish", etc)

"Blockr", a block-explorer service, also offers this functionality even tough they don't have an API: https://btc.blockr.io/tx/push

Why isn't BlockTrail under "High-level wallet APIs"? They have a wallet function and everything Blockchain.info has.

As far as I can see, they have a data API just like everyone else. Actually, I thought about removing the "high-level wallet API". I fail to see the advantage over just having your own wallet, and using one of the many data APIs to process payments.

Not sure if this would fall under High-level wallet API but Block.io (https://block.io) seems to be another service offering some APIs. I haven't looked at the docs yet but heard about them a couple times in the past few days.

what exactly do these limits at BlockTrail mean?


Does it mean, that my application is only allowed to check for one transaction in one second?

Assumed i have an online shop, and 4 customers send 4 payments at the same time, then i will be able to check only for the confirmation of one payment out of 4 at once?

What are the costs for the "Pro" package?

No. You can only make one request per second. Please check their page for knowing the rates.

well but thats the point, what is meant by "request"?

A request is a http request, that means, a single call to their API per second. Your example might still work if they allow to check multiple addresses etc in a single request. But yes, most likely you'll need the pro package.

BTW, Hello block is not available anymore. Unfortunately, because they were the only ones apart from Toshi that passed my list-of-unspents test. :\

I removed them from the list.

Added block.io, a high-level wallet provider that supports multisig

Just discovered https://github.com/bitpay/bitcore-node, which seems to be a more focused successor of BitPay's insight API using their "bitcore" API (http://bitcore.io/guide/). Looks pretty nice, if you're aiming at self-hosting!

Wow. It looks great. I got my node blockchain up to date so it might be a good time to try this one out. Thanks for it!

Seems like a total memory muncher, though. Always crashed on my machine due to low memory, but I was running insight in parallel  ::)

Still wondering why anyone would do a database in nodejs...

Would love to see a list of differences for bitcore-node vs. insight, for now it seems a bit like a copy.

It's maybe worth mentioning here that BlockTrail now implements a 'Fair Use Policy' - so it's totally FREE


https://i.imgur.com/4GMRLFy.png


https://www.blocktrail.com/pricing

Any chance Blocktrail will offer these two functionalities?

1. Get tx data: given a tx hash, return its hex data (also for unconfirmed txs). (edit: sorry, I noticed this was already in the 'Get Transaction' function, as 'raw')
2. Push tx: given a tx (as hex data), push or broadcast it to the network.

I love blocktrail (my absolute #1 preferred API) but I really miss these two functions.

While I'm at it, something else that would be great as well:

3. Get tx propagation: given an unconfirmed tx hash, returns an estimate % of nodes that have this tx in their mempool.

BlockTrail has a `push tx` endpoint, the documentation is lacking a bit behind on some of the new features added;
https://api.blocktrail.com/v1/BTC/send-raw-tx?api_key
either POST a raw hex or JSON {hex: <rawhex>}

While you are here: out of curiosity, is Blocktrail based on bitcoin core (with heavy extensions on top of it, of course), based on a different client (eg, btcd) or completely custom?

BlockTrail is based on bitcoin core with heavy extensions, yes.

This is one of the reasons we were able to maintain all of our infrastructure (block explorer, API's, etc) on the correct chain, which in turn, left our users happy.

Yes, that is certainly an advantage over using a custom software directly. Thanks for replying!

We have just launched a new block explorer - smartbit.com.au (https://www.smartbit.com.au/)

Our launch thread can be found here: https://bitcointalk.org/index.php?topic=1127817.0 (https://bitcointalk.org/index.php?topic=1127817.0)

A snippet of the API calls available:

Address with the biggest balance: https://api.smartbit.com.au/v1/blockchain/addresses?sort=balance&limit=1 (https://api.smartbit.com.au/v1/blockchain/addresses?sort=balance&limit=1)
Address with the most transactions: https://api.smartbit.com.au/v1/blockchain/addresses?sort=transaction_count&limit=1 (https://api.smartbit.com.au/v1/blockchain/addresses?sort=transaction_count&limit=1)
Combined address balance with transactions (wallet style result): https://api.smartbit.com.au/v1/blockchain/address/3A1KUd5H4hBEHk4bZB4C3hGgvuXuVX7p7t,39coweGgC8CPZ6hYL1BBEfc1zqbSfHsprW/wallet (https://api.smartbit.com.au/v1/blockchain/address/3A1KUd5H4hBEHk4bZB4C3hGgvuXuVX7p7t,39coweGgC8CPZ6hYL1BBEfc1zqbSfHsprW/wallet)
Block with the most transactions: https://api.smartbit.com.au/v1/blockchain/blocks?sort=transaction_count&limit=1 (https://api.smartbit.com.au/v1/blockchain/blocks?sort=transaction_count&limit=1)
Get op-returns for a block: https://api.smartbit.com.au/v1/blockchain/block/365956/op-returns (https://api.smartbit.com.au/v1/blockchain/block/365956/op-returns)
Information on a mining pool and their mined blocks: https://api.smartbit.com.au/v1/blockchain/pool/BitFury (https://api.smartbit.com.au/v1/blockchain/pool/BitFury)
Open assets: https://api.smartbit.com.au/v1/blockchain/op-returns/open-asset (https://api.smartbit.com.au/v1/blockchain/op-returns/open-asset)
Proof of existence: https://api.smartbit.com.au/v1/blockchain/op-returns/proof-of-existence (https://api.smartbit.com.au/v1/blockchain/op-returns/proof-of-existence)
Find output script types eg. multisig: https://api.smartbit.com.au/v1/blockchain/scripts/multisig (https://api.smartbit.com.au/v1/blockchain/scripts/multisig)
Find document hash via search: https://api.smartbit.com.au/v1/blockchain/search?q=8b03d5236a840e37c50c83c83e71e42eaee0230e4e4ac7889cde92d1cb1d25e9 (https://api.smartbit.com.au/v1/blockchain/search?q=8b03d5236a840e37c50c83c83e71e42eaee0230e4e4ac7889cde92d1cb1d25e9)

Cheers!

I added you to the list. Let me know if there's anything missing.

Just to add on to Charles comment Smartbit has the following features as well

1. Get tx data: given a tx hash, return its hex data (also for unconfirmed txs).

Couple options. For example here's how to to get the hex, based on the transaction hash :
https://www.smartbit.com.au/tx/bf3c9cf049c360fcd9e6af9e730478e0de5563167e283bfb29e8b012ae53b747/hex (https://www.smartbit.com.au/tx/bf3c9cf049c360fcd9e6af9e730478e0de5563167e283bfb29e8b012ae53b747/hex)
https://api.smartbit.com.au/v1/blockchain/transaction/e0d4d2f1ec598fe237dced2132ed8e978da9f4708884b87a41e898b74a835fc1/hex
 (https://api.smartbit.com.au/v1/blockchain/transaction/e0d4d2f1ec598fe237dced2132ed8e978da9f4708884b87a41e898b74a835fc1/hex)
You can also decode the hex and get the response directly from bitcoin core which is quite cool!
https://www.smartbit.com.au/txs/decodetx (https://www.smartbit.com.au/txs/decodetx)

Or you can use the API to decode via POST (See API Playground)
https://api.smartbit.com.au/v1/blockchain/decodetx (https://api.smartbit.com.au/v1/blockchain/decodetx)


2. Push tx: given a tx (as hex data), push or broadcast it to the network.

Just paste the hex in here:
https://www.smartbit.com.au/txs/pushtx (https://www.smartbit.com.au/txs/pushtx)
Or API as  POST method
https://api.smartbit.com.au/v1/blockchain/pushtx


If the hex is already in the blockchain, the api will respond with the relevant transaction id.

3. Get tx propagation: given an unconfirmed tx hash, returns an estimate % of nodes that have this tx in their mempool.

Smartbit has transaction propagation % across the network. You can see this live on any unconfirmed transaction.

Find a unconfirmed transaction here and go to its detail page. You'll see the propagtion percentage as its picked up across the network.
https://www.smartbit.com.au/txs/unconfirmed (https://www.smartbit.com.au/txs/unconfirmed)
https://api.smartbit.com.au/v1/blockchain/transaction/e0d4d2f1ec598fe237dced2132ed8e978da9f4708884b87a41e898b74a835fc1 (https://api.smartbit.com.au/v1/blockchain/transaction/e0d4d2f1ec598fe237dced2132ed8e978da9f4708884b87a41e898b74a835fc1)

The propagation field on the API is (along with double_spend).
"propagation": "1.0000",
"double_spend": false,

If more than one transaction tries to re spend an unspent transaction output, we'll flag the transaction as a double spend.


We've also built an API Playground. The playground allows anyone to interact with the API, changing any variables, and seeing the response via the interface. Perfect for testing and understanding how the Data API and websockets calls work.

API Playground here:

https://www.smartbit.com.au/docs


Would appreciate knowing if anyone uses the API Playground and feedback you may have?

Great, thanks!

Wow, looks great! Both the web explorer as well as the API.
Also thanks to jspri3 for the detailed examples. Good stuff!

Yep, no problem! If you or anyone else for that matter have any more questions you can always PM me. Thanks  :D

I've got another question :)

Does BlockTrail have a function (either in the API, or through the web UI) to decode a raw transaction (hex data) back into json data with inputs and outputs etc?
I mean something like http://btc.blockr.io/tx/push or https://blockchain.info/decode-tx or the decodetx function in smartbit's API (https://www.smartbit.com.au/docs).

Note that I can't always use a txid here, it has to be raw tx data, as this would also be used to verify or inspect txs before pushing them to the network.

We recommend using a library to do so instead of using an API, it's faster and more reliable.
Our own SDKs use the following libs and we'd recommend these to anyone (we're also co-maintainers on these);

 - PHP: https://github.com/Bit-Wasp/bitcoin-lib-php (functional) or https://github.com/Bit-Wasp/bitcoin-php (OOP)
 - NodeJS: github.com/bitcoinjs/bitcoinjs-lib
 - Python: https://github.com/petertodd/python-bitcoinlib

Right, yes, I didn't think of that but good point. I'll look into the SDKs you suggested. Thx again!

No problem. Let me know if you have any more questions.

Added bitgo and gem for high-level wallet providers.

Any reason as to why Blocktrail is not there? We provide multi-sig, HD and webhooks.

I am currently a bit unsure how to categorize the different bitcoin APIs and wallet services.
I should maybe revisit my categorization criteria and redo this list - at the moment it's a bit
vague. For example, your services provides obviously more integrated/high-level features than
a typical "data API" provider such as chain.com, but it's less high-level that for example
BitGo, right?

So maybe I'll just redo this list in form of a table of features rather than making up categories
that are to some extend arbitrary.

I am open for ideas - maybe a website would be a better option?

Please consider adding blockonomics api to the list https://www.blockonomics.co/views/api.html

- Thanks

It's as high level as BitGo.

You could try making a website I guess.