RNA Structure Toolkit
Enter a sequence, fold it, and render the secondary structure as an interactive force-directed diagram. For publication-grade minimum-free-energy folds, send the sequence to the official ViennaRNA server and paste the result back.
Letters only. T is converted to U; anything outside A/C/G/U is removed.
Quick fold runs a Turner-2004 nearest-neighbour energy minimization (the same Zuker algorithm and energy model as ViennaRNA RNAfold) directly in your browser — pseudoknot-free. It reproduces RNAfold's default output on our test sequences; for publication-grade results the official server on the right remains authoritative.
Real minimum-free-energy folding can't run on this page, so fold on the source and paste the dot-bracket structure back here to render it exactly.
Drag nucleotides to rearrange · scroll to zoom · press c to center.
Rendered with fornac.
Quick fold implements the Zuker minimum-free-energy algorithm with the Turner 2004
nearest-neighbour energy model (stacking, hairpin, bulge, internal & multi-loop energies, special
tri/tetra/hexa-loops, and the default -d2 dangling-end treatment). The energy parameters were extracted
from the ViennaRNA Package, so on our validation set it reproduces RNAfold's default MFE structures
exactly (e.g. GGGAGAGCC…CGUCCC → (((((((.(((((....)))))...))).)))),
ΔG = −11.1 kcal/mol). It is pseudoknot-free and runs to ~800 nt in-browser.
Accurate fold relies on the ViennaRNA RNAfold web server (Turner 2004 energy model) or mfold/UNAFold. Paste the returned dot-bracket string into box 2 to render the exact structure here.
Visualization uses fornac, the browser-native successor to VARNA from the same group (VARNA itself is a Java application and can no longer run inside web browsers).
CTAATACGACTCACTATA
← T7 promoter (always on)