Stellar was made to support digital representations of any currency, but it also has its own built-in token, called the lumen, created to fill a special role in the network. By design, Stellar requires that each account hold a small number of lumens at all times.
This lumen requirement is modest—a few is more than enough for most accounts. The full technical details are covered in Stellar’s docs, but, below, we explore some high-level concepts.
The need for lumens arose out of the fundamental design of Stellar’s ledger system. Simply put, it’s too easy to use. Without some nominal barrier or cost, the ledger could become filled with spam or nonsense, or used as a kind of arbitrary database system. These outcomes would defeat the intent behind Stellar: to be a fast, efficient payments system.
To solve this, we needed to introduce just the slightest bit of friction to deter bad or frivolous actors. Imposing a minimum balance on each account and a very small per-transaction fee were chosen as these deterrent costs. Right now, the minimum balance is 1 lumen and the minimum per-transaction fee is 0.00001 lumen. These are small enough to keep Stellar widely accessible, but big enough to discourage large-scale bad behavior.
Since Stellar is a universal system for digital money, we could’ve allowed people to pay these costs in dollars, pesos, yuan or anything else. But we felt none of these were appropriate. First, we didn’t want the network to “prefer” any particular national currency—if Stellar used dollars, say, then network prices would stay fixed for Americans but float for everyone else. And, even more, we wanted to create a digital-first asset that embraces the openness of the internet and is independent of economic and political factors.
So we gave the network its own currency, intended solely for denominating network requirements. That currency is “the lumen.” As you can see below, there are now 4.3 million Stellar accounts, and each of them uses lumens to meet minimum balance requirements and pay transactions fees.
A natural, pleasant, byproduct of having a network token is that it eases the movement of money between users. Because everyone has and needs lumens, lumens can always be a medium of exchange between otherwise illiquid assets.
The lumen supply
Unlike the tokens of other blockchains, lumens aren’t mined or awarded by the protocol over time. Instead, 100 billion lumens were created when the Stellar network went live, and for the first 5 or so years of Stellar’s existence, the supply of lumens also increased by 1% annually, by design.
That inflation mechanism was ended by community vote in October 2019. And in November 2019, the overall lumen supply was reduced. Now there are about 50 billion lumens, total, in existence, and no more lumens will be created.
Nearly 20 billion lumens are out in the open market, and the Stellar Development Foundation retains the other 30 billion or so to develop and promote Stellar, per its mandate. Those lumens will enter the public markets over the next few years. Anyone who wants a complete accounting for all lumens in existence should visit our Lumen Accounting guide for detailed explanations of major lumen metrics, as well as instructions on how to calculate supply details from the ground-up using Stellar’s APIs.
How to buy and store lumens
You need lumens to use Stellar. Luckily, they’re for sale on many exchanges and available for trade directly on the Stellar network as well.
In the U.S., Coinbase and Kraken are two options for buying lumens with dollars. The native Stellar exchange, Lobstr, allows you to buy lumens directly on the network. See our longer list of lumen-supporting exchanges for more options.
Note that digital currencies can be volatile and buying them can be risky. While lumens will always have utility in the Stellar network, the price of lumens denominated in fiat currency may change, and you could lose significant value.
For storing lumens and for easy access to network features like payments and peer-to-peer sends, we recommend a hardware or digital wallet from our wallets list.