To every complex-oriented ring spectrum $E$ there is associated a formal group law, which is a power series $F\_E(x,y)\in E\_\*[[x,y]]$.


Suppose $E$ and $F$ are two complex-oriented ring spectra and suppose I have an isomorphism of coefficient rings $\phi:E\_\*\rightarrow F\_\*$ that carries $F\_E(x,y)$ to $F\_F(x,y)$.


Does this imply that $E$ and $F$ are homotopy equivalent spectra?


Note that if $F\_E(x,y)$ and $F\_F(x,y)$ are "Landweber exact" formal group laws then the answer is yes.



Are complex-oriented ring spectra determined by their formal group law?
The following is a communal answer from the algebraic topology Discord [[1](http://nodorek.net)], primarily put forward by Irakli Patchkoria (correcting previous half-answers by Tyler Lawson and me).
Kiran suggested it be recorded here to ease future reference.


The idea is to produce two topological realizations $M$, $N$ of a single $MU\_\*$–module by finding two distinct resolutions whose effect on homotopy is the same.
The two associated square-zero extensions then give a counterexample.
We'll reduce complexity first by considering $ku$–modules rather than $MU$–modules, and second by aiming for a $ku$–module whose homotopy cleaves into small even and odd parts, forcing its $ku\_\*$–module structure to trivialize.


$\DeclareMathOperator{\Sq}{Sq}
\newcommand{\F}{\mathbb{F}}
\newcommand{\Z}{\mathbb{Z}}
\newcommand{\HFtwo}{H\F\_2}
\newcommand{\Susp}{\Sigma}
\newcommand{\co}{\colon\thinspace}$
The nice homotopy groups of complex $K$–theory, $ku\_\* = \Z[u]$, can be used to show that its bottom $k$–invariant $\kappa\_{ku}$ is $ku$–linear: in the diagram
$$
\begin{array}{ccccc}
& & \Susp^4 ku \\
& & u \downarrow \\
\Susp^{-1} H\Z & \to & \Susp^2 ku & \to & \Susp^2 H\Z \\
& & u \downarrow \\
& & ku & \to & H\Z,
\end{array}
$$
the vertical maps are multiplication by homotopy elements, hence are $ku$–linear; in turn the horizontal co/fibers are also $ku$–linear; and, finally, the $k$–invariant appears as the middle composite, hence is also $ku$–linear.
Similarly, we can show the $ku$–linearity of the bottom $k$–invariant of $ku/2$ and of the Bockstein map $\beta\co \HFtwo \to \Susp H\Z$ (relying on the $ku$–linearity of $2\co H\Z \to H\Z$).


Stringing some of these together gives a $ku$–linear composite $$\HFtwo \xrightarrow{\kappa\_{ku/2}} \Susp^3 \HFtwo \xrightarrow{\beta} \Susp^4 H\Z \to \Susp^4 \HFtwo.$$
The bottom $k$–invariant $\kappa\_{ku/2}$ of $ku/2$ is given as the Milnor primitive $Q\_2 = \Sq^3 + \Sq^2 \Sq^1$, the composite of the latter two maps is given as $\Sq^1$, and hence the whole composite is the nontrivial Steenrod operation $$\Sq^1 Q\_2 = \Sq^1(\Sq^3 + \Sq^2 \Sq^1) = \Sq^3 \Sq^1.$$
Meanwhile, the homotopy groups of the cofiber $M$ of this composite are $\Susp \F\_2 \oplus \Susp^4 \F\_2$, which splits as a $ku\_\*$–module — hence this $ku\_\*$–module could alternatively be modeled by $N = \Susp H\F\_2 \oplus \Susp^4 \HFtwo$ (i.e., the cofiber of the zero map).
To finish, set $E = ku \oplus M$ and $F = ku \oplus N$.


