diff --git a/Cargo.toml b/Cargo.toml
index b97cbf9..2ff1eb8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -16,6 +16,7 @@ crate-type = ["cdylib", "lib", "staticlib"]
 rand = "0.4"
 bit-vec = "0.4.4"
 futures = "0.1"
+cfg-if = "0.1.7"
 
 pairing = { git = 'https://github.com/matterinc/pairing', tag = "0.16.2" }
 #pairing = { path = "../pairing" }
@@ -26,6 +27,7 @@ num_cpus = {version = "1", optional = true}
 crossbeam = {version = "0.7.1", optional = true}
 
 tiny-keccak = {version = "1.4.2", optional = true}
+web-sys = {version = "0.3.17", optional = true, features = ["console", "Performance", "Window"]}
 
 [dependencies.blake2-rfc]
 git = "https://github.com/gtank/blake2-rfc"
@@ -34,8 +36,8 @@ rev = "7a5b5fc99ae483a0043db7547fb79a6fa44b88a9"
 [features]
 default = ["multicore"]
 #default = ["multicore", "gm17", "sonic"]
-#default = ["singlecore"]
+#default = ["wasm"]
 multicore = ["futures-cpupool", "num_cpus", "crossbeam"]
 sonic = ["tiny-keccak"]
 gm17 = []
-singlecore = []
+wasm = ["web-sys"]
diff --git a/src/groth16/generator.rs b/src/groth16/generator.rs
index 3d4cb1f..961696a 100644
--- a/src/groth16/generator.rs
+++ b/src/groth16/generator.rs
@@ -1,4 +1,4 @@
-use super::super::verbose_flag;
+use crate::log::Stopwatch;
 
 use rand::Rng;
 
@@ -187,8 +187,6 @@ pub fn generate_parameters<E, C>(
 ) -> Result<Parameters<E>, SynthesisError>
     where E: Engine, C: Circuit<E>
 {
-    let verbose = verbose_flag();
-
     let mut assembly = KeypairAssembly {
         num_inputs: 0,
         num_aux: 0,
@@ -217,7 +215,7 @@ pub fn generate_parameters<E, C>(
         );
     }
 
-    if verbose {eprintln!("Making {} powers of tau", assembly.num_constraints)};
+    elog_verbose!("Making {} powers of tau", assembly.num_constraints);
     // Create bases for blind evaluation of polynomials at tau
     let powers_of_tau = vec![Scalar::<E>(E::Fr::zero()); assembly.num_constraints];
     let mut powers_of_tau = EvaluationDomain::from_coeffs(powers_of_tau)?;
@@ -250,9 +248,9 @@ pub fn generate_parameters<E, C>(
     let mut h = vec![E::G1::zero(); powers_of_tau.as_ref().len() - 1];
     {
         // Compute powers of tau
-        if verbose {eprintln!("computing powers of tau...")};
+        elog_verbose!("computing powers of tau...");
 
-        let start = std::time::Instant::now();
+        let stopwatch = Stopwatch::new();
 
         {
             let powers_of_tau = powers_of_tau.as_mut();
@@ -270,15 +268,15 @@ pub fn generate_parameters<E, C>(
                 }
             });
         }
-        if verbose {eprintln!("powers of tau stage 1 done in {} s", start.elapsed().as_millis() as f64 / 1000.0);};
+        elog_verbose!("powers of tau stage 1 done in {} s", stopwatch.elapsed());
 
         // coeff = t(x) / delta
         let mut coeff = powers_of_tau.z(&tau);
         coeff.mul_assign(&delta_inverse);
 
-        if verbose {eprintln!("computing the H query with multiple threads...")};
+        elog_verbose!("computing the H query with multiple threads...");
 
-        let start = std::time::Instant::now();
+        let stopwatch = Stopwatch::new();
 
         // Compute the H query with multiple threads
         worker.scope(h.len(), |scope, chunk| {
@@ -302,27 +300,26 @@ pub fn generate_parameters<E, C>(
                 });
             }
         });
-        if verbose {eprintln!("computing the H query done in {} s", start.elapsed().as_millis() as f64 / 1000.0);};
+        elog_verbose!("computing the H query done in {} s", stopwatch.elapsed());
     }
 
-    if verbose {eprintln!("using inverse FFT to convert powers of tau to Lagrange coefficients...")};
-    
-    let start = std::time::Instant::now();
+    elog_verbose!("using inverse FFT to convert powers of tau to Lagrange coefficients...");
+
+    let stopwatch = Stopwatch::new();
 
     // Use inverse FFT to convert powers of tau to Lagrange coefficients
     powers_of_tau.ifft(&worker);
     let powers_of_tau = powers_of_tau.into_coeffs();
 
-    if verbose {eprintln!("powers of tau stage 2 done in {} s", start.elapsed().as_millis() as f64 / 1000.0)};
-
+    elog_verbose!("powers of tau stage 2 done in {} s", stopwatch.elapsed());
     let mut a = vec![E::G1::zero(); assembly.num_inputs + assembly.num_aux];
     let mut b_g1 = vec![E::G1::zero(); assembly.num_inputs + assembly.num_aux];
     let mut b_g2 = vec![E::G2::zero(); assembly.num_inputs + assembly.num_aux];
     let mut ic = vec![E::G1::zero(); assembly.num_inputs];
     let mut l = vec![E::G1::zero(); assembly.num_aux];
 
-    if verbose {eprintln!("evaluating polynomials...")};
-    let start = std::time::Instant::now();
+    elog_verbose!("evaluating polynomials...");
+    let stopwatch = Stopwatch::new();
 
     fn eval<E: Engine>(
         // wNAF window tables
@@ -475,7 +472,7 @@ pub fn generate_parameters<E, C>(
         &worker
     );
 
-    if verbose {eprintln!("evaluating polynomials done in {} s", start.elapsed().as_millis() as f64 / 1000.0);};
+    elog_verbose!("evaluating polynomials done in {} s", stopwatch.elapsed());
 
     // Don't allow any elements be unconstrained, so that
     // the L query is always fully dense.
@@ -498,7 +495,7 @@ pub fn generate_parameters<E, C>(
         ic: ic.into_iter().map(|e| e.into_affine()).collect()
     };
 
-    println!("Has generated {} points", a.len());
+    log!("Has generated {} points", a.len());
 
     Ok(Parameters {
         vk: vk,
diff --git a/src/groth16/prover.rs b/src/groth16/prover.rs
index 3c7412c..86981e2 100644
--- a/src/groth16/prover.rs
+++ b/src/groth16/prover.rs
@@ -1,4 +1,4 @@
-use super::super::verbose_flag;
+use crate::log::Stopwatch;
 
 use rand::Rng;
 
@@ -164,20 +164,18 @@ impl<E:Engine> PreparedProver<E> {
         s: E::Fr
     ) -> Result<Proof<E>, SynthesisError>
     {
-        let verbose = verbose_flag();
-
         let prover = self.assignment.clone();
         let worker = Worker::new();
 
         let vk = params.get_vk(self.assignment.input_assignment.len())?;
 
-        let start = std::time::Instant::now();
+        let stopwatch = Stopwatch::new();
 
         let h = {
             let mut a = EvaluationDomain::from_coeffs(prover.a)?;
             let mut b = EvaluationDomain::from_coeffs(prover.b)?;
             let mut c = EvaluationDomain::from_coeffs(prover.c)?;
-            if verbose {eprintln!("H query domain size is {}", a.as_ref().len())};
+            elog_verbose!("H query domain size is {}", a.as_ref().len());
 
             // here a coset is a domain where denominator (z) does not vanish
             // inverse FFT is an interpolation
@@ -209,9 +207,9 @@ impl<E:Engine> PreparedProver<E> {
             multiexp(&worker, params.get_h(a.len())?, FullDensity, a)
         };
 
-        if verbose {eprintln!("{} seconds for prover for H evaluation (mostly FFT)", start.elapsed().as_millis() as f64 / 1000.0)};
+        elog_verbose!("{} seconds for prover for H evaluation (mostly FFT)", stopwatch.elapsed());
 
-        let start = std::time::Instant::now();
+        let stopwatch = Stopwatch::new();
 
         // TODO: Check that difference in operations for different chunks is small
 
@@ -222,9 +220,8 @@ impl<E:Engine> PreparedProver<E> {
 
         let input_len = input_assignment.len();
         let aux_len = aux_assignment.len();
-        if verbose {eprintln!("H query is dense in G1,\nOther queries are {} elements in G1 and {} elements in G2",
-            2*(input_len + aux_len) + aux_len, input_len + aux_len)
-        };
+        elog_verbose!("H query is dense in G1,\nOther queries are {} elements in G1 and {} elements in G2",
+            2*(input_len + aux_len) + aux_len, input_len + aux_len);
 
         // Run a dedicated process for dense vector
         let l = multiexp(&worker, params.get_l(aux_assignment.len())?, FullDensity, aux_assignment.clone());
@@ -287,7 +284,7 @@ impl<E:Engine> PreparedProver<E> {
         g_c.add_assign(&h.wait()?);
         g_c.add_assign(&l.wait()?);
 
-        if verbose {eprintln!("{} seconds for prover for point multiplication", start.elapsed().as_millis() as f64 / 1000.0)};
+        elog_verbose!("{} seconds for prover for point multiplication", stopwatch.elapsed());
 
         Ok(Proof {
             a: g_a.into_affine(),
@@ -411,8 +408,6 @@ pub fn create_proof<E, C, P: ParameterSource<E>>(
 ) -> Result<Proof<E>, SynthesisError>
     where E: Engine, C: Circuit<E>
 {
-    let verbose = verbose_flag();
-
     let mut prover = ProvingAssignment {
         a_aux_density: DensityTracker::new(),
         b_input_density: DensityTracker::new(),
@@ -440,13 +435,13 @@ pub fn create_proof<E, C, P: ParameterSource<E>>(
 
     let vk = params.get_vk(prover.input_assignment.len())?;
 
-    let start = std::time::Instant::now();
+    let stopwatch = Stopwatch::new();
 
     let h = {
         let mut a = EvaluationDomain::from_coeffs(prover.a)?;
         let mut b = EvaluationDomain::from_coeffs(prover.b)?;
         let mut c = EvaluationDomain::from_coeffs(prover.c)?;
-        if verbose {eprintln!("H query domain size is {}", a.as_ref().len())};
+        elog_verbose!("H query domain size is {}", a.as_ref().len());
         // here a coset is a domain where denominator (z) does not vanish
         // inverse FFT is an interpolation
         a.ifft(&worker);
@@ -477,9 +472,9 @@ pub fn create_proof<E, C, P: ParameterSource<E>>(
         multiexp(&worker, params.get_h(a.len())?, FullDensity, a)
     };
 
-    if verbose {eprintln!("{} seconds for prover for H evaluation (mostly FFT)", start.elapsed().as_millis() as f64 / 1000.0)};
+    elog_verbose!("{} seconds for prover for H evaluation (mostly FFT)", stopwatch.elapsed());
 
-    let start = std::time::Instant::now();
+    let stopwatch = Stopwatch::new();
 
     // TODO: Check that difference in operations for different chunks is small
 
@@ -549,7 +544,7 @@ pub fn create_proof<E, C, P: ParameterSource<E>>(
     g_c.add_assign(&h.wait()?);
     g_c.add_assign(&l.wait()?);
 
-    if verbose {eprintln!("{} seconds for prover for point multiplication", start.elapsed().as_millis() as f64 / 1000.0)};
+    elog_verbose!("{} seconds for prover for point multiplication", stopwatch.elapsed());
 
     Ok(Proof {
         a: g_a.into_affine(),
diff --git a/src/lib.rs b/src/lib.rs
index 690219a..f730ec4 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,10 +1,16 @@
 #![allow(unused_imports)]
+#![allow(unused_macros)]
+#[macro_use]
 
+extern crate cfg_if;
 extern crate pairing as pairing_import;
 extern crate rand;
 extern crate bit_vec;
 extern crate byteorder;
 
+#[macro_use]
+mod log;
+
 pub mod domain;
 pub mod groth16;
 
@@ -20,18 +26,21 @@ mod multiexp;
 #[cfg(test)]
 mod tests;
 
-#[cfg(feature = "multicore")]
-mod multicore;
+cfg_if! {
+    if #[cfg(feature = "multicore")] {
+        #[cfg(feature = "wasm")]
+        compile_error!("Multicore feature is not yet compatible with wasm target arch");
 
-#[cfg(feature = "singlecore")]
-mod singlecore;
-
-mod worker {
-    #[cfg(feature = "multicore")]
-    pub use crate::multicore::*;
-
-    #[cfg(feature = "singlecore")]
-    pub use crate::singlecore::*;
+        mod multicore;
+        mod worker {
+            pub use crate::multicore::*;
+        }
+    } else {
+        mod singlecore;
+        mod worker {
+            pub use crate::singlecore::*;
+        }
+    }
 }
 
 pub mod pairing {
@@ -41,6 +50,7 @@ pub mod pairing {
 mod cs;
 pub use self::cs::*;
 
+// todo move to log module after removing all references
 static mut VERBOSE_SWITCH: i8 = -1;
 
 use std::str::FromStr;
diff --git a/src/log.rs b/src/log.rs
new file mode 100644
index 0000000..b912a16
--- /dev/null
+++ b/src/log.rs
@@ -0,0 +1,70 @@
+#[allow(unused_macros)]
+
+cfg_if! {
+    if #[cfg(feature = "wasm")] {
+        use web_sys;
+        use web_sys::Performance;
+
+        macro_rules! log {
+            ($($t:tt)*) => (web_sys::console::log_1(&format_args!($($t)*).to_string().into()))
+        }
+
+        macro_rules! elog {
+            ($($t:tt)*) => (web_sys::console::log_1(&format_args!($($t)*).to_string().into()))
+        }
+
+        macro_rules! log_verbose {
+            ($($t:tt)*) => (if $crate::verbose_flag() { web_sys::console::log_1(&format_args!($($t)*).to_string().into()) })
+        }
+
+        macro_rules! elog_verbose {
+            ($($t:tt)*) => (if $crate::verbose_flag() { web_sys::console::log_1(&format_args!($($t)*).to_string().into()) })
+        }
+
+        pub struct Stopwatch {
+            start: f64,
+            perf: Performance
+        }
+
+        impl Stopwatch {
+            pub fn new() -> Stopwatch {
+                let perf = web_sys::window().unwrap().performance().unwrap();
+                Stopwatch { start: perf.now(), perf }
+            }
+
+            pub fn elapsed(&self) -> f64 {
+                (self.perf.now() - self.start) / 1000.0
+            }
+        }
+    } else {
+        macro_rules! log {
+            ($($t:tt)*) => (println!($($t)*))
+        }
+
+        macro_rules! elog {
+            ($($t:tt)*) => (eprintln!($($t)*))
+        }
+
+        macro_rules! log_verbose {
+            ($($t:tt)*) => (if $crate::verbose_flag() { println!($($t)*) })
+        }
+
+        macro_rules! elog_verbose {
+            ($($t:tt)*) => (if $crate::verbose_flag() { eprintln!($($t)*) })
+        }
+
+        pub struct Stopwatch {
+            start: std::time::Instant
+        }
+
+        impl Stopwatch {
+            pub fn new() -> Stopwatch {
+                Stopwatch { start: std::time::Instant::now() }
+            }
+
+            pub fn elapsed(&self) -> f64 {
+                self.start.elapsed().as_millis() as f64 / 1000.0
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/singlecore.rs b/src/singlecore.rs
index df73c80..816ceef 100644
--- a/src/singlecore.rs
+++ b/src/singlecore.rs
@@ -16,7 +16,7 @@ impl Worker {
     // We don't expose this outside the library so that
     // all `Worker` instances have the same number of
     // CPUs configured.
-    pub(crate) fn new_with_cpus(cpus: usize) -> Worker {
+    pub(crate) fn new_with_cpus(_cpus: usize) -> Worker {
         Worker {
             cpus: 1,
         }